An unusual unit of measurement is a
unit of measurement
A unit of measurement is a definite magnitude of a quantity, defined and adopted by convention or by law, that is used as a standard for measurement of the same kind of quantity. Any other quantity of that kind can be expressed as a multi ...
that does not form part of a coherent
system of measurement
A system of measurement is a collection of units of measurement and rules relating them to each other. Systems of measurement have historically been important, regulated and defined for the purposes of science and commerce. Systems of measurement i ...
, especially because its exact quantity may not be well known or because it may be an inconvenient multiple or fraction of a base unit.
This definition is not exact since it includes units such as the ''week'' or the ''
light-year'', which are quite "usual" in the sense that they are often used, but can be "unusual" if taken out of their common context, as demonstrated by the
furlong-firkin-fortnight (FFF) system of units.
Many of the unusual units of measurements listed here are colloquial measurements, units devised to compare a measurement to common and familiar objects.
Length
Hammer unit
Valve's Source
Source may refer to:
Research
* Historical document
* Historical source
* Source (intelligence) or sub source, typically a confidential provider of non open-source intelligence
* Source (journalism), a person, publication, publishing institute o ...
game engine uses the ''Hammer unit'' as its base unit of length. This unit refers to Source's official map creation software, Hammer. The exact definition varies from game to game, but a Hammer unit is usually defined as a sixteenth of a foot (16 Hammer units = 1 foot). This means that 1 Hammer unit is equal to exactly 0.01905 meters.
Rack unit
![Server rack rail dimensions](https://upload.wikimedia.org/wikipedia/commons/a/a9/Server_rack_rail_dimensions.svg)
One ''rack unit'' (U) is and is used to measure rack-mountable audiovisual, computing and industrial equipment. Rack units are typically denoted without a space between the number of units and the 'U'. Thus a 4U
server
Server may refer to:
Computing
*Server (computing), a computer program or a device that provides functionality for other programs or devices, called clients
Role
* Waiting staff, those who work at a restaurant or a bar attending customers and su ...
enclosure (case) is high, or more practically, built to occupy a vertical space seven inches high, with sufficient clearance to allow movement of adjacent hardware.
Hand
The ''hand'' is a non-
SI unit of length equal to exactly . It is normally used to measure the height of horses in some English-speaking countries, including Australia, Canada, Ireland, the United Kingdom, and the United States.
Light-nanosecond
![Grace Murray Hopper visualizing nanoseconds](https://upload.wikimedia.org/wikipedia/commons/1/1b/Grace_Murray_Hopper_visualizing_nanoseconds.png)
The light-nanosecond is defined as exactly 29.9792458 cm. It was popularized in
information technology
Information technology (IT) is the use of computers to create, process, store, retrieve, and exchange all kinds of Data (computing), data . and information. IT forms part of information and communications technology (ICT). An information te ...
as a unit of distance by
Grace Hopper
Grace Brewster Hopper (; December 9, 1906 – January 1, 1992) was an American computer scientist, mathematician, and United States Navy rear admiral. One of the first programmers of the Harvard Mark I computer, she was a pioneer of compu ...
as the distance which a photon could travel in one billionth of a second (roughly 30 cm or one foot): "The
speed of light
The speed of light in vacuum, commonly denoted , is a universal physical constant that is important in many areas of physics. The speed of light is exactly equal to ). According to the special theory of relativity, is the upper limit ...
is one foot per nanosecond."
Metric feet
A
metric foot
ISO 2848 (''Building construction – Modular coordination – Principles and rules)'' is an international standard for the construction industry that describes the aims of modular coordination and gives the rules to be used in establishing the di ...
, defined as ), has been used occasionally in the UK but has never been an official unit.
A
Chinese foot is defined as around one third of a meter, depending on jurisdiction.
Horse
Horses are used to measure distances in
horse racing – a ''horse length'' (shortened to merely a ''length'' when the context makes it obvious) equals roughly . Shorter distances are measured in fractions of a ''horse length''; also common are measurements of a full or fraction of a ''head'', a ''neck'', or a ''nose''.
Boat length
In rowing races such as the
Oxford and Cambridge Boat Race
The Boat Race is an annual set of rowing races between the Cambridge University Boat Club and the Oxford University Boat Club, traditionally rowed between open-weight eights on the River Thames in London, England. There are separate men' ...
, the margin of victory and of defeat is expressed in fractions and multiples of ''boat lengths''. The length of a
rowing eight is about . A shorter distance is the ''
canvas'', which is the length of the covered part of the boat between the bow and the bow oarsman. The
Racing Rules of Sailing
The Racing Rules of Sailing (often abbreviated to RRS) govern the conduct of yacht racing, windsurfing, kitesurfing, model boat racing, dinghy racing and virtually any other form of racing around a course with more than one vessel while powered b ...
also makes heavy use of boat lengths.
Football field (length)
A football field is often used as a comparative measurement of length when talking about distances that may be hard to comprehend when stated in terms of standard units.
An
American football field
The rectangular field of play used for American football games measures long between the goal lines, and (53.3 yards) wide. The field may be made of grass or artificial turf. In addition, there are end zones extending another past the goal li ...
is usually understood to be long, though it is technically when including the two long end zones. The field is wide.
An
association football pitch may vary within limits of in length and in width. The usual size of a football pitch is , the dimensions used for matches in the
UEFA Champions League
The UEFA Champions League (abbreviated as UCL, or sometimes, UEFA CL) is an annual club football competition organised by the Union of European Football Associations (UEFA) and contested by top-division European clubs, deciding the competi ...
.
A
Canadian football field
Canadian football () is a sport played in Canada in which two teams of 12 players each compete for territorial control of a field of play long and wide attempting to advance a pointed oval-shaped ball into the opposing team's scoring area (e ...
is wide and long, including two long end zones.
Block
In most US cities, a
city block is between . In
Manhattan
Manhattan (), known regionally as the City, is the most densely populated and geographically smallest of the five boroughs of New York City. The borough is also coextensive with New York County, one of the original counties of the U.S. state ...
, the measurement "block" usually refers to a north–south block, which is . Sometimes people living in places (like Manhattan) with a regularly spaced street grid will speak of ''long blocks'' and ''short blocks''. Within a typical large North American city, it is often only possible to travel along east–west and north–south streets, so travel distance between two points is often given in the number of blocks east–west plus the number north–south (known to mathematicians as the ''
Manhattan Metric'').
Earth
Radius
The radius of Earth, generally given as 6,371 kilometers (3,959 miles) is often employed as a unit of measure to intuitively compare objects of planetary size.
Lunar distance
Lunar distance (LD), the distance from the center of Earth to the center of the Moon, is a unit of measure in astronomy. The lunar distance is approximately , or 1.28
light-second
The light-second is a unit of length useful in astronomy, telecommunications and relativistic physics. It is defined as the distance that light travels in free space in one second, and is equal to exactly .
Just as the second forms the basis for ...
s; this is roughly 30 times
Earth's diameter. A little less than 400 lunar distances make up an
astronomical unit
The astronomical unit (symbol: au, or or AU) is a unit of length, roughly the distance from Earth to the Sun and approximately equal to or 8.3 light-minutes. The actual distance from Earth to the Sun varies by about 3% as Earth orbits ...
.
Siriometer
The
siriometer is an obsolete astronomical measure equal to one million
astronomical unit
The astronomical unit (symbol: au, or or AU) is a unit of length, roughly the distance from Earth to the Sun and approximately equal to or 8.3 light-minutes. The actual distance from Earth to the Sun varies by about 3% as Earth orbits ...
s, i.e., one million times the average distance between the Sun and Earth.
This distance is equal to about 15.8
light-years, 149.6
Pm, or 4.8
parsec
The parsec (symbol: pc) is a unit of length used to measure the large distances to astronomical objects outside the Solar System, approximately equal to or (au), i.e. . The parsec unit is obtained by the use of parallax and trigonometry, an ...
s, and is about twice the distance from Earth to the star
Sirius
Sirius is the brightest star in the night sky. Its name is derived from the Greek word , or , meaning 'glowing' or 'scorching'. The star is designated α Canis Majoris, Latinized to Alpha Canis Majoris, and abbreviated Alpha CM ...
.
Area
Barn
One barn is 10
−28 square meters, about the cross-sectional area of a uranium nucleus. The name probably derives from early neutron-deflection experiments, when the uranium nucleus was described, and the phrases "big as a barn" and "hit a barn door" were used. Barn are typically used for
cross section
Cross section may refer to:
* Cross section (geometry)
** Cross-sectional views in architecture & engineering 3D
*Cross section (geology)
* Cross section (electronics)
* Radar cross section, measure of detectability
* Cross section (physics)
**Abs ...
s in nuclear and particle physics. Additional units include the microbarn (or "outhouse") and the yoctobarn (or "shed").
Brass
One brass is exactly area (used in measurement of work done or to be done, such as plastering, painting, etc.). It is also equal, however, to of estimated or supplied loose material, such as sand, gravel, rubble, etc. This unit is prevalent in the construction industry in
India
India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the seventh-largest country by area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the so ...
.
Square
The ''
square
In Euclidean geometry, a square is a regular quadrilateral, which means that it has four equal sides and four equal angles (90- degree angles, π/2 radian angles, or right angles). It can also be defined as a rectangle with two equal-length a ...
'' is an
Imperial unit
The imperial system of units, imperial system or imperial units (also known as British Imperial or Exchequer Standards of 1826) is the system of units first defined in the British Weights and Measures Act 1824 and continued to be developed thr ...
of
area
Area is the quantity that expresses the extent of a region on the plane or on a curved surface. The area of a plane region or ''plane area'' refers to the area of a shape or planar lamina, while '' surface area'' refers to the area of an ope ...
that is used in the construction industry in North America, and was historically used in
Australia by real estate agents. One square is equal to . A
roof
A roof ( : roofs or rooves) is the top covering of a building, including all materials and constructions necessary to support it on the walls of the building or on uprights, providing protection against rain, snow, sunlight, extremes of te ...
's area may be calculated in square feet, then converted to squares.
Cow's grass
In Ireland, before the 19th century, a "cow's grass" was a measurement used by farmers to indicate the size of their fields. A cow's grass was equal to the amount of land that could produce enough grass to support a cow.
Football field (area)
![Terrains de polo et de football (US compliant)](https://upload.wikimedia.org/wikipedia/commons/4/46/Terrains_de_polo_et_de_football_%28US_compliant%29.svg)
A
football pitch
A football pitch (also known as soccer field) is the playing surface for the game of association football. Its dimensions and markings are defined by Law 1 of the Laws of the Game, "The Field of Play". The pitch is typically made of natural t ...
, or field, can be used as a man-in-the-street unit of area. The standard
FIFA football pitch
A football pitch (also known as soccer field) is the playing surface for the game of association football. Its dimensions and markings are defined by Law 1 of the Laws of the Game, "The Field of Play". The pitch is typically made of natural t ...
is long by wide (); FIFA allows for a variance of up to in length and in width in either direction (and even larger discretions if the pitch is not used for international competition), which generally results in the association football pitch generally only being used for
order of magnitude
An order of magnitude is an approximation of the logarithm of a value relative to some contextually understood reference value, usually 10, interpreted as the base of the logarithm and the representative of values of magnitude one. Logarithmic di ...
comparisons.
An
American football field
The rectangular field of play used for American football games measures long between the goal lines, and (53.3 yards) wide. The field may be made of grass or artificial turf. In addition, there are end zones extending another past the goal li ...
, including both end zones, is , or (). A
Canadian football field
Canadian football () is a sport played in Canada in which two teams of 12 players each compete for territorial control of a field of play long and wide attempting to advance a pointed oval-shaped ball into the opposing team's scoring area (e ...
is wide and long with end zones adding a combined to the length, making it or .
An
Australian rules football field
Australian(s) may refer to:
Australia
* Australia, a country
* Australians, citizens of the Commonwealth of Australia
** European Australians
** Anglo-Celtic Australians, Australians descended principally from British colonists
** Aboriginal Aus ...
may be approximately (or more) long goal to goal and (or more) wide, although the field's elliptical nature reduces its area to a certain extent. A football field has an area of approximately , twice the area of a Canadian football field and three times that of an American football field.
Morgen
A
morgen
A morgen was a unit of measurement of land area in Germany, the Netherlands, Poland, Lithuania and the Dutch colonies, including South Africa and Taiwan. The size of a morgen varies from . It was also used in Old Prussia, in the Balkans, Norw ...
("morning" in Dutch and German) was approximately the amount of land tillable by one man behind an ox in the morning hours of a day. This was an official unit of measurement in South Africa until the 1970s, and was defined in November 2007 by the South African Law Society as having a conversion factor of 1 morgen = . This unit of measure was also used in the Dutch colonial province of
New Netherland
New Netherland ( nl, Nieuw Nederland; la, Novum Belgium or ) was a 17th-century colonial province of the Dutch Republic that was located on the east coast of what is now the United States. The claimed territories extended from the Delmarva P ...
(later
New York and parts of
New England
New England is a region comprising six states in the Northeastern United States: Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island, and Vermont. It is bordered by the state of New York (state), New York to the west and by the Can ...
).
Countries, regions, and cities
![British Isles United Kingdom WA highlighted](https://upload.wikimedia.org/wikipedia/commons/1/13/British_Isles_United_Kingdom_WA_highlighted.svg)
The area of a familiar country, state or city is often used as a unit of measure, especially in
journalism
Journalism is the production and distribution of reports on the interaction of events, facts, ideas, and people that are the " news of the day" and that informs society to at least some degree. The word, a noun, applies to the occupation (pro ...
.
Wales
Equal to 20,779 km
2 (8,023 sq mi), the country of
Wales
Wales ( cy, Cymru ) is a country that is part of the United Kingdom. It is bordered by England to the east, the Irish Sea to the north and west, the Celtic Sea to the south west and the Bristol Channel to the south. It had a population in ...
is used in phrases such as "an area the size of Wales" or "twice the area of Wales".
England
England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe b ...
is 6.275 times the size of Wales, and Scotland is roughly four times the size of Wales.
Ireland
Ireland ( ; ga, Éire ; Ulster Scots dialect, Ulster-Scots: ) is an island in the Atlantic Ocean, North Atlantic Ocean, in Northwestern Europe, north-western Europe. It is separated from Great Britain to its east by the North Channel (Grea ...
is four times as large as Wales, and
France
France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of overseas regions and territories in the Americas and the Atlantic, Pacific and Indian Oceans. Its metropolitan area ...
is about twenty-five times larger.
The British comedy show ''
The Eleven O'Clock Show
''The 11 O'Clock Show'' is a satirical late-night British television comedy series on Channel 4 which featured topical sketches and commentary on news items. It ran between 30 September 1998 and 8 December 2000, most notably hosted by Iain Lee a ...
'' parodied the use of this measurement, by introducing a news article about an earthquake in Wales, stating that an area the size of Wales was affected. The Radio 4 programme ''More or Less'' introduced the idea of "kilowales" – an area 1,000 times the size of Wales. ''
The Register
''The Register'' is a British technology news website co-founded in 1994 by Mike Magee, John Lettice and Ross Alderson. The online newspaper's masthead sublogo is "''Biting the hand that feeds IT''." Their primary focus is information te ...
'' introduced the nanowales (20.78 m
2).
The measurement has been adopted by rainforest conservation charity
Size of Wales
Size of Wales is a climate change charity with the aim of conserving an area of tropical rainforest twice the size of Wales. The project currently supports 7 forest protection projects and 1 tree planting project across Africa and South Ameri ...
, aiming to conserve an area of rainforest equating to the area of Wales. On 1 March 2013, the
charity
Charity may refer to:
Giving
* Charitable organization or charity, a non-profit organization whose primary objectives are philanthropy and social well-being of persons
* Charity (practice), the practice of being benevolent, giving and sharing
* C ...
announced that they had succeeded in conserving an area of rainforest the size of Wales and will continue to operate to sustain and increase the protected area.
United States
In the United States, the area of the smallest state,
Rhode Island
Rhode Island (, like ''road'') is a state in the New England region of the Northeastern United States. It is the smallest U.S. state by area and the seventh-least populous, with slightly fewer than 1.1 million residents as of 2020, but it ...
(); the largest of the contiguous 48 states,
Texas
Texas (, ; Spanish: ''Texas'', ''Tejas'') is a state in the South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2020, it is the second-largest U.S. state by ...
(); and less commonly
Alaska
Alaska ( ; russian: Аляска, Alyaska; ale, Alax̂sxax̂; ; ems, Alas'kaaq; Yup'ik: ''Alaskaq''; tli, Anáaski) is a state located in the Western United States on the northwest extremity of North America. A semi-exclave of the U.S. ...
(), the largest of all 50 states, are used in a similar fashion. For example,
Antarctica
Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean, it contains the geographic South Pole. Antarctica is the fifth-largest cont ...
's
Larsen B ice shelf
The Larsen Ice Shelf is a long ice shelf in the northwest part of the Weddell Sea, extending along the east coast of the Antarctic Peninsula from Cape Longing to Smith Peninsula. It is named after Captain Carl Anton Larsen, the master of the N ...
was approximately the size of Rhode Island until it broke up in 2002. Other areas may be described like this, too, like in the 1979 movie ''
The China Syndrome
''The China Syndrome'' is a 1979 American disaster thriller film directed by James Bridges and written by Bridges, Mike Gray, and T. S. Cook. The film stars Jane Fonda, Jack Lemmon, Michael Douglas (who also produced), Scott Brady, James ...
'' when radiation is expected to contaminate "an area the size of
Pennsylvania
Pennsylvania (; ( Pennsylvania Dutch: )), officially the Commonwealth of Pennsylvania, is a state spanning the Mid-Atlantic, Northeastern, Appalachian, and Great Lakes regions of the United States. It borders Delaware to its southeast, ...
".
The US
Central Intelligence Agency
The Central Intelligence Agency (CIA ), known informally as the Agency and historically as the Company, is a civilian foreign intelligence service of the federal government of the United States, officially tasked with gathering, processing, ...
uses
Washington, D.C.
)
, image_skyline =
, image_caption = Clockwise from top left: the Washington Monument and Lincoln Memorial on the National Mall, United States Capitol, Logan Circle, Jefferson Memorial, White House, Adams Morgan, ...
() as a comparison for city-sized objects.
Other countries
In the Netherlands, its smallest province,
Utrecht
Utrecht ( , , ) is the fourth-largest city and a municipality of the Netherlands, capital and most populous city of the province of Utrecht. It is located in the eastern corner of the Randstad conurbation, in the very centre of mainland Net ...
(), is often used as a comparison for regions in general.
The country of
Belgium
Belgium, ; french: Belgique ; german: Belgien officially the Kingdom of Belgium, is a country in Northwestern Europe. The country is bordered by the Netherlands to the north, Germany to the east, Luxembourg to the southeast, France to th ...
() has also often been used when comparing areas, to the point where it has been regarded as a
meme and where there is
websitededicated to notable areas which have been compared to that of Belgium.
The
Isle of Wight
The Isle of Wight ( ) is a Counties of England, county in the English Channel, off the coast of Hampshire, from which it is separated by the Solent. It is the List of islands of England#Largest islands, largest and List of islands of England#Mo ...
(), an island off the south coast of mainland
England
England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe b ...
, is commonly used to define smaller areas. It has sometimes been used in attempts to examine whether a certain amount of a given object or group would fit in a space its size; in 2018, it was estimated that approximately 2.6 billion people could fit on the Isle of Wight, at a population density of six people per square metre.
In
Denmark
)
, song = ( en, "King Christian stood by the lofty mast")
, song_type = National and royal anthem
, image_map = EU-Denmark.svg
, map_caption =
, subdivision_type = Sovereign state
, subdivision_name = Kingdom of Denmark
, establish ...
, the island of
Bornholm () is often used to describe the size of an area.
In Germany, the
Saarland
The Saarland (, ; french: Sarre ) is a state of Germany in the south west of the country. With an area of and population of 990,509 in 2018, it is the smallest German state in area apart from the city-states of Berlin, Bremen, and Hamburg, and ...
() is often used to define areas.
In
Brazil
Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...
, it is common to compare relatively small areas to the state of
Sergipe
Sergipe (), officially State of Sergipe, is a state of Brazil. Located in the Northeast Region along the Atlantic coast of the country, Sergipe is the smallest state in Brazil by geographical area at , larger only than the Federal District. Serg ...
(), the smallest in the country. Smaller areas are sometimes compared to the cities of
São Paulo
São Paulo (, ; Portuguese for ' Saint Paul') is the most populous city in Brazil, and is the capital of the state of São Paulo, the most populous and wealthiest Brazilian state, located in the country's Southeast Region. Listed by the Ga ...
() or
Rio de Janeiro
Rio de Janeiro ( , , ; literally 'River of January'), or simply Rio, is the capital of the state of the same name, Brazil's third-most populous state, and the second-most populous city in Brazil, after São Paulo. Listed by the GaWC as a ...
().
Volume
Metric ounce
A metric ounce is an approximation of the imperial ounce, US dry ounce, or US fluid ounce. These three customary units vary. However, the metric ounce is usually taken as 25 or 30 ml when volume is being measured, or grams when mass is being measured.
The US
Food and Drug Administration
The United States Food and Drug Administration (FDA or US FDA) is a List of United States federal agencies, federal agency of the United States Department of Health and Human Services, Department of Health and Human Services. The FDA is respon ...
(FDA) defines the "food labeling ounce" as 30 ml, slightly larger than the 29.6 ml
fluid ounce
A fluid ounce (abbreviated fl oz, fl. oz. or oz. fl., old forms ℥, fl ℥, f℥, ƒ ℥) is a unit of volume (also called ''capacity'') typically used for measuring liquids. The British Imperial, the United States customary, and the United ...
.
Several
Dutch units of measurement
The Dutch units of measurement used today are those of the metric system. Before the 19th century, a wide variety of different weights and measures were used by the various Dutch towns and provinces. Despite the country's small size, there was a l ...
have been replaced with informal metric equivalents, including the ''ons'' or ounce. It originally meant of a pound, or a little over 30 grams depending on which definition of the pound was used, but was redefined as 100 grams when the country metricated.
Shot
![Three shotglasses](https://upload.wikimedia.org/wikipedia/commons/f/fb/Three_shotglasses.jpg)
The
shot
Shot may refer to:
Arts, entertainment, and media
* ''Shot'' (album), by The Jesus Lizard
*''Shot, Illusion, New God'', an EP by Gruntruck
*'' Shot Rev 2.0'', a video album by The Sisters of Mercy
* "Shot" (song), by The Rasmus
* ''Shot'' (2017 f ...
is a liquid volume measure that varies from country to country and state to state depending on legislation. It is routinely used for measuring strong
liquor or spirits when the amount served and consumed is smaller than the more common measures of alcoholic "drink" and "pint". There is a legally defined maximum size of a serving in some jurisdictions. The size of a "single" shot is . The smaller "pony" shot is . According to Encyclopædia Britannica Almanac 2009, a pony is 0.75
fluid ounce
A fluid ounce (abbreviated fl oz, fl. oz. or oz. fl., old forms ℥, fl ℥, f℥, ƒ ℥) is a unit of volume (also called ''capacity'') typically used for measuring liquids. The British Imperial, the United States customary, and the United ...
s of liquor.
According to
Wolfram Alpha
WolframAlpha ( ) is an answer engine developed by Wolfram Research. It answers factual queries by computing answers from externally sourced data.
WolframAlpha was released on May 18, 2009 and is based on Wolfram's earlier product Wolfram Mat ...
, one pony is 1
U.S. fluid ounce.
"Double" shots (surprisingly not always the size of two single shots, even in the same place) are . In the UK, spirits are sold in shots of either 25 ml (approximating the old
fluid ounce
A fluid ounce (abbreviated fl oz, fl. oz. or oz. fl., old forms ℥, fl ℥, f℥, ƒ ℥) is a unit of volume (also called ''capacity'') typically used for measuring liquids. The British Imperial, the United States customary, and the United ...
) or 35 ml.
Board foot or super foot
A board foot is a United States and Canadian unit of approximate volume, used for lumber. It is equivalent to (). It is also found in the unit of density ''pounds per board foot''. In Australia and New Zealand the terms ''super foot'' or ''superficial foot'' were formerly used for this unit. The exact volume of wood specified is variable and depends on the type of lumber. For planed lumber the dimensions used to calculate board feet are
nominal dimensions, which are larger than the actual size of the planed boards. See
Dimensional lumber
Lumber is wood that has been processed into dimensional lumber, including beams and planks or boards, a stage in the process of wood production. Lumber is mainly used for construction framing, as well as finishing (floors, wall panels, wi ...
for more information on this.
Hoppus foot
A system of measure for timber in the round (standing or felled), now largely superseded by the metric system except in measuring hardwoods in certain countries. Its purpose is to estimate the value of sawn timber in a log, by measuring the unsawn log and allowing for wastage in the mill. Following the so-called "quarter-girth formula" (the square of one quarter of the circumference in inches multiplied by of the length in feet), the notional log is four feet in circumference, one inch of which yields the hoppus board foot, 1 foot yields the hoppus foot, and 50 feet yields a hoppus ton. This translates to a hoppus foot being equal to . The hoppus board foot, when milled, yields about one
board foot
The board foot or board-foot is a unit of measurement for the volume of lumber in the United States and Canada. It equals the volume of a length of a board, one foot wide and thick.
Board foot can be abbreviated as FBM (for "foot, board measure" ...
. The volume yielded by the quarter-girth formula is 78.54% of cubic measure (i.e. 1 ft
3 = 0.7854 h ft; 1 h ft = 1.273 ft
3).
Cubic ton
A cubic ton is an antiquated measure of volume, varying based on the commodity from about . It is now only used for lumber, for which one cubic ton is equivalent to .
Cord and rick
![Cord of wood](https://upload.wikimedia.org/wikipedia/commons/c/c7/Cord_of_wood.jpg)
The cord is a unit of measure of
dry volume
Dry measures are units of volume to measure bulk commodities that are not fluids and that were typically shipped and sold in standardized containers such as barrels. They have largely been replaced by the units used for measuring volumes in the met ...
used in Canada and the United States to measure
firewood and
pulpwood. A cord is the amount of wood that, when "ranked and well stowed" (arranged so pieces are aligned, parallel, touching and compact), occupies a volume of . This corresponds to a well-stacked woodpile, 4 feet deep by 4 feet high by 8 feet wide , or any other arrangement of linear measurements that yields the same volume. A more unusual measurement for firewood is the "rick" or
face cord
A face cord is an informal measurement for stacked firewood, sometimes called a rick.
Width and height is typically the same as a cord
Cord or CORD may refer to:
People
* Alex Cord (1933–2021), American actor and writer
* Chris Cord (born 19 ...
. It is stacked deep with the other measurements kept the same as a cord, making it of a cord; however, regional variations mean that its precise definition is non-standardized.
Twenty-foot equivalent unit
The twenty-foot equivalent unit is the volume of the smallest standard
shipping container
A shipping container is a container with strength suitable to withstand shipment, storage, and handling. Shipping containers range from large reusable steel boxes used for intermodal shipments to the ubiquitous corrugated boxes. In the context of ...
. It is equivalent to . Larger intermodal containers are commonly described in multiples of TEU, as are container ship capacities.
Acre-foot
An acre-foot is a unit of volume commonly used in the United States in reference to large-scale water resources, such as reservoirs, aqueducts, canals, sewer flow capacity, irrigation water and river flows. It is defined by the volume of one acre of surface area to a depth of one foot. .
Casual units
![Olympic Swimming Pool - Fast Lane](https://upload.wikimedia.org/wikipedia/commons/e/e1/Olympic_Swimming_Pool_-_Fast_Lane.JPG)
Many well-known objects are regularly used as casual units of volume. They include:
Double-decker bus. The approximate volume of a
double-decker bus
A double-decker bus or double-deck bus is a bus that has two storeys or decks. They are used for mass transport in the United Kingdom, the United States, New Zealand, Europe, Asia and also in cities such as Sydney; the best-known example is the ...
, abbreviated to DDB, has been used informally to describe the size of hole created by a major sewer collapse. For example, a report might refer to "a 4 DDB hole".
Olympic-size swimming pool. For larger volumes of liquid, one measure commonly used in the media in many countries is the
Olympic-size swimming pool
An Olympic-size swimming pool conforms to regulated dimensions that are large enough for international competition. This type of swimming pool is used in the Olympic Games, where the race course is in length, typically referred to as "long cour ...
. A Olympic swimming pool, built to the FR3 minimum depth of would hold . The US
National Institute of Standards and Technology
The National Institute of Standards and Technology (NIST) is an agency of the United States Department of Commerce whose mission is to promote American innovation and industrial competitiveness. NIST's activities are organized into physical s ...
(NIST) defines the Olympic swimming pool as 1 million litres, which is the approximate volume of the smaller FR2 pool.
Royal Albert Hall. The
Royal Albert Hall, a large concert hall, is sometimes used as a unit of volume in the UK, for example when referring to volumes of rubbish placed in landfill. It is famously used in the line "Now they know how many holes it takes to fill the Albert Hall." in
The Beatles
The Beatles were an English rock band, formed in Liverpool in 1960, that comprised John Lennon, Paul McCartney, George Harrison and Ringo Starr. They are regarded as the most influential band of all time and were integral to the developmen ...
song "
A Day in the Life".
The volume of the auditorium is between 3 and 3.5 million cubic feet (between 85,000 and 99,000 cubic metres).
Melbourne Cricket Ground. A common measure of volume in
Australia, and in the state of
Victoria
Victoria most commonly refers to:
* Victoria (Australia), a state of the Commonwealth of Australia
* Victoria, British Columbia, provincial capital of British Columbia, Canada
* Victoria (mythology), Roman goddess of Victory
* Victoria, Seychelle ...
in particular, is the
Melbourne Cricket Ground, the largest stadium in Australia and
13th largest in the world. The volume of the Melbourne Cricket Ground is 1,574,000 cubic metres, or about 630
Olympic swimming pools. Its seating capacity (100,000 ) is also used as a unit measure of the
number of people.
![Sydney(from air) V2](https://upload.wikimedia.org/wikipedia/commons/d/d4/Sydney%28from_air%29_V2.jpg)
Sydney Harbour. A unit of volume used in Australia for water. One Sydney Harbour is the amount of water in
Sydney Harbour: approximately 562 gigalitres (562,000,000 cubic metres, or 0.562 of a cubic
kilometre); or in terms of the more unusual measures above, about 357
Melbourne Cricket Grounds, 238,000
Olympic Swimming pools, or 476,000
acre-feet
The acre-foot is a non- SI unit of volume equal to about commonly used in the United States in reference to large-scale water resources, such as reservoirs, aqueducts, canals, sewer flow capacity, irrigation water, and river flows.
An acre-f ...
.
The Grand Canyon. With a volume measure approximately 4 orders of magnitude greater than Sydney Harbour, the volume of the
Grand Canyon may be used to visualize even larger things, like the magma chamber underneath Yellowstone and other things. According to the
National Park Service
The National Park Service (NPS) is an agency of the United States federal government within the U.S. Department of the Interior that manages all national parks, most national monuments, and other natural, historical, and recreational propert ...
, the volume of the Grand Canyon is which is ().
Flow rate
Miner's inch
The volume of water which flows in one unit of time through an orifice of one square inch area. The size of the unit varies from one place to another.
Mass
Electronvolt mass
It is common in particle physics to use eV/''c''
2 as a unit of mass. Here, eV (electronvolt) is a unit of energy (the kinetic energy of an
electron
The electron ( or ) is a subatomic particle with a negative one elementary electric charge. Electrons belong to the first generation of the lepton particle family,
and are generally thought to be elementary particles because they have no ...
accelerated over one
volt
The volt (symbol: V) is the unit of electric potential, electric potential difference (voltage), and electromotive force in the International System of Units (SI). It is named after the Italian physicist Alessandro Volta (1745–1827).
Defin ...
,
joule
The joule ( , ; symbol: J) is the unit of energy in the International System of Units (SI). It is equal to the amount of work done when a force of 1 newton displaces a mass through a distance of 1 metre in the direction of the force applie ...
s), and ''c'' is the speed of light in a vacuum. Energy and mass are related through ''E'' = ''mc''
2. This definition is useful for a
linear particle accelerator
A linear particle accelerator (often shortened to linac) is a type of particle accelerator that accelerates charged subatomic particles or ions to a high speed by subjecting them to a series of oscillating electric potentials along a linear b ...
when accelerating electrons.
In many systems of
natural units
In physics, natural units are physical units of measurement in which only universal physical constants are used as defining constants, such that each of these constants acts as a coherent unit of a quantity. For example, the elementary charge ma ...
, so the ''c'' is dropped and eV itself becomes a unit of mass.
Bag of cement and bag mix
The mass of an old bag of
cement
A cement is a binder, a chemical substance used for construction that sets, hardens, and adheres to other materials to bind them together. Cement is seldom used on its own, but rather to bind sand and gravel ( aggregate) together. Cement mi ...
was one
hundredweight
The hundredweight (abbreviation: cwt), formerly also known as the centum weight or quintal, is a British imperial and US customary unit of weight or mass. Its value differs between the US and British imperial systems. The two values are distingu ...
~ 112 lb, approximately 50 kg. The amount of material that, say, an aircraft could carry into the air is often visualised as the number of bags of cement that it could lift. In the concrete and petroleum industry, however, a bag of cement is defined as 94 pounds (~ 42.6 kg), because it has an apparent volume close to . When
ready-mix concrete
Ready-mix concrete (RMC) is concrete that is manufactured in a batch plant, according to each specific job requirement, then delivered to the job site "ready to use".
There are two types with the first being the barrel truck or in–trans ...
is specified, a "bag mix" unit is used as if the batching company mixes 5 literal bags of cement per cubic yard (or cubic metre) when a "5 bag mix" is ordered.
Grave
In 1793, the French term "
grave
A grave is a location where a dead body (typically that of a human, although sometimes that of an animal) is buried or interred after a funeral. Graves are usually located in special areas set aside for the purpose of burial, such as grav ...
" (from "gravity") was suggested as the base unit of mass for the metric system. In 1795, however, the name "
kilogramme
The kilogram (also kilogramme) is the unit of mass in the International System of Units (SI), having the unit symbol kg. It is a widely used measure in science, engineering and commerce worldwide, and is often simply called a kilo colloquially. ...
" was adopted instead.
Jupiter
When reporting on the masses of
extrasolar planet
An exoplanet or extrasolar planet is a planet outside the Solar System. The first possible evidence of an exoplanet was noted in 1917 but was not recognized as such. The first confirmation of detection occurred in 1992. A different planet, init ...
s, astronomers often discuss them in terms of multiples of
Jupiter's mass ( = 1.9 kg). For example, "Astronomers recently discovered a planet outside our Solar System with a mass of approximately 3 Jupiters." Furthermore, the mass of Jupiter is nearly equal to one thousandth of the mass of the Sun.
Sun
Solar mass ( = ) is also often used in astronomy when talking about masses of stars or galaxies; for example,
Alpha Centauri A has the mass of 1.1 suns, and the
Milky Way
The Milky Way is the galaxy that includes our Solar System, with the name describing the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye. ...
has a mass of approximately .
Solar mass also has a special use when estimating orbital periods and distances of 2 bodies using
Kepler's laws
In astronomy, Kepler's laws of planetary motion, published by Johannes Kepler between 1609 and 1619, describe the orbits of planets around the Sun. The laws modified the heliocentric theory of Nicolaus Copernicus, replacing its circular orbi ...
: ''a
3 = M
totalT
2'', where ''a'' is length of
semi-major axis in
AU, ''T'' is orbital period in years and ''M
total'' is the combined mass of objects in . In case of planet orbiting a star, ''M
total'' can be approximated to mean the mass of the central object. More specifically in the case of Sun and Earth the numbers reduce to ''M
total'' ~ 1, ''a'' ~ 1 and ''T'' ~ 1.
Time
Light-distance
George Gamow
George Gamow (March 4, 1904 – August 19, 1968), born Georgiy Antonovich Gamov ( uk, Георгій Антонович Гамов, russian: Георгий Антонович Гамов), was a Russian-born Soviet and American polymath, theoret ...
discussed measurements of time such as the "light-mile" and "light-foot", the time taken for light to travel the specified unit distance, defined by "reversing the procedure" used in defining a light-year. A light-foot is roughly one
nanosecond
A nanosecond (ns) is a unit of time in the International System of Units (SI) equal to one billionth of a second, that is, of a second, or 10 seconds.
The term combines the SI prefix ''nano-'' indicating a 1 billionth submultiple of an SI unit ( ...
.
Shake
In
nuclear engineering and astrophysics contexts, the
shake is sometimes used as a conveniently short period of time. 1 shake is defined as 10
nanosecond
A nanosecond (ns) is a unit of time in the International System of Units (SI) equal to one billionth of a second, that is, of a second, or 10 seconds.
The term combines the SI prefix ''nano-'' indicating a 1 billionth submultiple of an SI unit ( ...
s.
Jiffy
In
computing
Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It includes the study and experimentation of algorithmic processes, and development of both hardware and software. Computing has scientific, ...
, the
jiffy is the duration of one tick of the system timer
interrupt
In digital computers, an interrupt (sometimes referred to as a trap) is a request for the processor to ''interrupt'' currently executing code (when permitted), so that the event can be processed in a timely manner. If the request is accepted, ...
. Typically, this time is 0.01 seconds, though in some earlier systems (such as the
Commodore
Commodore may refer to:
Ranks
* Commodore (rank), a naval rank
** Commodore (Royal Navy), in the United Kingdom
** Commodore (United States)
** Commodore (Canada)
** Commodore (Finland)
** Commodore (Germany) or ''Kommodore''
* Air commodore ...
8-bit machines) the jiffy was defined as of a second, roughly equal to the vertical refresh period (i.e. the field rate) on
NTSC
The first American standard for analog television broadcast was developed by National Television System Committee (NTSC)National Television System Committee (1951–1953), Report and Reports of Panel No. 11, 11-A, 12–19, with Some supplement ...
video hardware (and the
period of AC electric power in North America).
Microfortnight
One unit derived from the
FFF system of units is the microfortnight, one millionth of the fundamental time unit of FFF, which equals 1.2096 seconds. This is a fairly representative example of "
hacker humor", and is occasionally used in operating systems; for example, the
OpenVMS TIMEPROMPTWAIT parameter is measured in microfortnights.
Sidereal day
The
sidereal day
Sidereal time (as a unit also sidereal day or sidereal rotation period) (sidereal ) is a timekeeping system that astronomers use to locate celestial objects. Using sidereal time, it is possible to easily point a telescope to the proper coor ...
is based on the Earth's rotation rate relative to fixed stars, rather than the Sun. A sidereal day is approximately 23 hours, 56 minutes, 4.0905 SI seconds.
Decimal time systems
![Decimal_Time_Clock](https://upload.wikimedia.org/wikipedia/commons/b/bf/Decimal_Time_Clock.jpeg)
The measurement of time is unique in SI in that while the
second is the base unit, and measurements of time smaller than a second use prefixed units smaller than a second (e.g. microsecond, nanosecond, etc.), measurements larger than a second instead use traditional divisions, including the
sexagesimal
Sexagesimal, also known as base 60 or sexagenary, is a numeral system with sixty as its base. It originated with the ancient Sumerians in the 3rd millennium BC, was passed down to the ancient Babylonians, and is still used—in a modified form ...
-based ''
minute'' and ''
hour'' as well as the less regular ''
day'' and ''
year
A year or annus is the orbital period of a planetary body, for example, the Earth, moving in its orbit around the Sun. Due to the Earth's axial tilt, the course of a year sees the passing of the seasons, marked by change in weather, the hou ...
'' units.
SI allows for the use of larger prefixed units based on the second, a system known as
metric time
Metric time is the measure of time intervals using the metric system. The modern SI system defines the second as the base unit of time, and forms multiples and submultiples with metric prefixes such as kiloseconds and milliseconds. Other unit ...
, but this is seldom used, since the number of seconds in a day (86,400 or,
in rare cases, 86,401) negate one of the metric system's primary advantages: easy conversion by multiplying or dividing by powers of ten.
There have been numerous proposals and usage of
decimal time
Decimal time is the representation of the time of day using units which are decimally related. This term is often used specifically to refer to the time system used in France for a few years beginning in 1792 during the French Revolution, whi ...
, most of which were based on the day as the base unit, such that the number of units between any two events that happen at the same time of day would be equal to the number of days between them multiplied by some integer power of ten. In dynastic China, the
kè was a unit that represented of a day (it has since been redefined to of a day, or 15 minutes). In France, a decimal time system in place from 1793 to 1805 divided the day into 10 hours, each divided into 100 minutes, in turn each divided into 100 seconds; the
French Republican Calendar further extended this by assembling days into ten-day "weeks".
Ordinal date
An ordinal date is a calendar date typically consisting of a ''year'' and a day of the year or ordinal day number (or simply ordinal day or day number), an ordinal number ranging between 1 and 366 (starting on January 1), though year may someti ...
s and
Julian days, the latter of which has seen use in astronomy as it is not subject to
leap year
A leap year (also known as an intercalary year or bissextile year) is a calendar year that contains an additional day (or, in the case of a lunisolar calendar, a month) added to keep the calendar year synchronized with the astronomical year or ...
complications, allow for the expression of a decimal portion of the day. In the mid-1960s, to defeat the advantage of the recently introduced computers for the then popular rally racing in the Midwest, competition lag times in a few events were given in centids ( day, 864 seconds, 14.4 minutes), millids ( day, 86.4 seconds), and centims ( minute, 0.6 seconds) the latter two looking and sounding a bit like the related units of minutes and seconds. Decimal time proposals are frequently used in fiction, often in
futuristic
The future is the time after the past and present. Its arrival is considered inevitable due to the existence of time and the laws of physics. Due to the apparent nature of reality and the unavoidability of the future, everything that currently ...
works.
In addition to decimal time, there also exist
binary clock
A binary clock is a clock that displays the time of day in a binary format. Originally, such clocks showed ''each decimal digit'' of sexagesimal time as a binary value, but presently binary clocks also exist which display hours, minutes, and se ...
s and
hexadecimal time
Hexadecimal time is the representation of the time of day as a hexadecimal number in the interval [0, 1).
The day is divided into 1016 (1610) hexadecimal hours, each hour into 10016 (25610) hexadecimal minutes, and each minute into 1016 ...
.
Sol
The United States-based NASA, when conducting missions to the planet Mars (planet), Mars, has typically used a time of day system calibrated to the mean solar day on that planet (known as a "sol"), training those involved on those missions to acclimate to that length of day, which is 88,775 SI seconds, or 2,375 seconds (about 39 minutes) longer than the mean solar day on Earth. NASA's Martian timekeeping system (instead of breaking down the sol into 25×53×67 or 25×67×53 SI second divisions) slows down clocks so that the 24-hour day is stretched to the length of that on Mars; Martian hours, minutes and seconds are thus 2.75% longer than their SI-compatible counterparts.
The
Darian calendar is an arrangement of sols into a Martian year. It maintains a seven-sol week (retaining Sunday through Saturday naming customs), with four weeks to a month and 24 months to a Martian year, which contains 668 or 669 sols depending on
leap year
A leap year (also known as an intercalary year or bissextile year) is a calendar year that contains an additional day (or, in the case of a lunisolar calendar, a month) added to keep the calendar year synchronized with the astronomical year or ...
s. The last Saturday of every six months is skipped over in the Darian calendar.
Dog year
![10 yr old Mastiff](https://upload.wikimedia.org/wikipedia/commons/5/58/10_yr_old_Mastiff.JPG)
There are two diametrically opposed definitions of the ''dog year'', primarily used to approximate the equivalent age of
dog
The dog (''Canis familiaris'' or ''Canis lupus familiaris'') is a domesticated descendant of the wolf. Also called the domestic dog, it is derived from the extinct Pleistocene wolf, and the modern wolf is the dog's nearest living relative. Do ...
s and other animals with similar life spans. Both are based upon a
popular myth regarding the
aging of dogs that states that a dog ages seven years in the time it takes a human to age one year.
*One seventh of a year, or approximately 52 days.
[Multimillionaire pooch dies at age 12 (84 in dog years)]
''MSNBC.com''. Retrieved 12 June 2011. When this definition is used, a standard calendar year is known as a "human year".
*A standard (365-day) calendar year of a dog's life, whereas a "human year" is the period of a dog's (or other animal's) life that is claimed to be equivalent to a year of a human being's life (or seven calendar years).
In fact, the aging of a dog varies by breed (larger breeds tend to have shorter lifespans than small and medium-sized breeds); dogs also develop faster and have longer adulthoods relative to their total life span than humans. Most dogs are sexually mature by 1 year old, which corresponds to perhaps 13 years old in humans.
Giant dog breed
A giant dog breed is a breed of dog of gigantic proportions, sometimes described as a breed whose weight exceeds . Breeds sometimes described as giant breeds include the Great Dane, Newfoundland, St. Bernard and Irish Wolfhound. These breeds hav ...
s and
bulldog
The Bulldog is a British breed of dog of mastiff type. It may also be known as the English Bulldog or British Bulldog. It is of medium size, a muscular, hefty dog with a wrinkled face and a distinctive pushed-in nose.[megaannum
A year or annus is the orbital period of a planetary body, for example, the Earth, moving in its orbit around the Sun. Due to the Earth's axial tilt, the course of a year sees the passing of the seasons, marked by change in weather, the hour ...]
or "Ma"). It is a convenient unit for long-term measurements. For example, oceans appeared on Earth after 4 GY, life is detectable at 5 GY, and multicellular organisms first appeared at 15 GY. The
age of the Earth is estimated at about 20 GY. This use of GY is not to be confused with Gyr for
gigayear
A billion years or giga-annum (109 years) is a unit of time on the petasecond scale, more precisely equal to seconds (or simply 1,000,000,000 years).
It is sometimes abbreviated Gy, Ga ("giga-annum"), Byr and variants. The abbreviations Gya o ...
or Gy for
Gray (unit).
KerMetric time
KerMetric time is a concept that divides the day into 100 equal parts called Kermits. Each Kermit is equivalent to 14.4 minutes. More precise time can be counted by dividing by 1000 or even 10000. The name Kermit came from a combination of the surname of the president of the
National Research Council National Research Council may refer to:
* National Research Council (Canada), sponsoring research and development
* National Research Council (Italy), scientific and technological research, Rome
* National Research Council (United States), part of ...
in 1983 (Dr.
Larkin Kerwin
John Larkin Kerwin (June 22, 1924 – May 1, 2004) was a Canadian physicist.
Born in Quebec City, he studied physics at St. Francis Xavier University and obtained his master's degree in physics at the Massachusetts Institute of Technology. H ...
). The original working model of KerMetric time as conceived by W. Thayer of NRC was assembled by the designated Clock Construction Team of John Phillips, Ron Hawkins, Les Moore and Willie Thayer in 1983.
Moment
A
moment was a
medieval
In the history of Europe, the Middle Ages or medieval period lasted approximately from the late 5th to the late 15th centuries, similar to the post-classical period of global history. It began with the fall of the Western Roman Empire ...
unit of time. The movement of a shadow on a
sundial covered 40 moments in a
solar hour. An hour in this case meant one twelfth of the period between
sunrise
Sunrise (or sunup) is the moment when the upper rim of the Sun appears on the horizon in the morning. The term can also refer to the entire process of the solar disk crossing the horizon and its accompanying atmospheric effects.
Terminology
A ...
and
sunset. The length of a
solar hour depended on the length of the day, which in turn varied with the
season
A season is a division of the year based on changes in weather, ecology, and the number of daylight hours in a given region. On Earth, seasons are the result of the axial parallelism of Earth's tilted orbit around the Sun. In temperate and ...
, so the length of a
moment in modern
seconds was not fixed, but on
average
In ordinary language, an average is a single number taken as representative of a list of numbers, usually the sum of the numbers divided by how many numbers are in the list (the arithmetic mean). For example, the average of the numbers 2, 3, 4, 7 ...
, a
moment corresponded to 90 seconds.
Thirds, fourths
The term "
minute" usually means of an
hour, coming from "a minute division of an hour". The term "
second" comes from "the
second minute division of an hour", as it is of a minute, or of of an hour. While usually sub-second units are represented with
SI prefixes on the second (e.g.
milliseconds), this system can be extrapolated further, such that a "Third" would mean of a second, and a "Fourth" would mean of a third, etc. These units are occasionally used in astronomy to denote angles.
Angular measure
Furman
The Furman is a unit of angular measure equal to of a circle, or just under 20
arcseconds. It is named for Alan T. Furman, the American mathematician who adapted the
CORDIC
CORDIC (for "coordinate rotation digital computer"), also known as Volder's algorithm, or: Digit-by-digit method Circular CORDIC (Jack E. Volder), Linear CORDIC, Hyperbolic CORDIC (John Stephen Walther), and Generalized Hyperbolic CORDIC (GH C ...
algorithm for 16-bit fixed-point arithmetic sometime around 1980. 16 bits give a resolution of 2
16 = 65,536 distinct angles.
Binary degree, binary radian, brad
A related unit of angular measure equal to of a circle, represented by 8 bits, has found some use in machinery control where fine precision is not required, most notably crankshaft and camshaft position in
internal combustion engine controllers, and in video game programming. There is no consensus as to its name, but it has been called the 8-Bit Furman, the Small Furman, the Furboy and more recently, the miFurman, (milli-binary-Furman). These units are convenient because they form cycles: for the 8-bit unit, the value overflows from 255 to 0 when a full circle has been traversed, so binary addition and subtraction work as expected. Measures are often made using a
Gray code, which is trivially converted into more conventional notation. Its value is equivalent to
Tau
Tau (uppercase Τ, lowercase τ, or \boldsymbol\tau; el, ταυ ) is the 19th letter of the Greek alphabet, representing the voiceless dental or alveolar plosive . In the system of Greek numerals, it has a value of 300.
The name in English ...
/256 radians, or about 0.0245436926 radians.
Grade ''(also grad, gradian, gon)''
Coordinates were measured in grades on official French terrestrial ordnance charts from the French revolution well into the 20th century. 1 grade (or in modern symbology, 1 gon) = 0.9° or 0.01 right angle. One advantage of this measure is that the distance between latitude lines 0.01 gon apart at the equator is almost exactly 1 kilometer ''(and would be exactly 1 km if the original definition of 1 meter = quarter-meridian had been adhered to)''. One disadvantage is that common angles like 30° and 60° are expressed by fractional values (33 and 66 respectively) so this "decimal" unit failed to displace the "sexagesimal" units equilateral-vertex – degree – minute – second invented by Babylonian astronomers.
Mils, strecks
![mil estimation](https://upload.wikimedia.org/wikipedia/commons/d/d1/Mil_estimation.jpg)
''Mils'' and ''strecks'' are small units of angle used by various military organizations for range estimation and translating map coordinates used for directing artillery fire. The exact size varies between different organizations: there are 6400 NATO mils per
turn (1 NATO mil = 0.982
mrad
The Barrett MRAD (Multi-role Adaptive Design) is a bolt-action sniper rifle designed by Barrett to meet the requirements of the SOCOM PSR. The MRAD is based on the Barrett 98B and includes a number of modifications and improvements. The Barret ...
), or 6000 Warsaw pact mils per turn (1 Warsaw pact mil = 1.047 mrad). In the Swedish military, there are 6300 strecks per turn (1 streck = 0.997 mrad).
MERU (Milli Earth Rate Unit)
The MERU, or Milli Earth Rate Unit, is an angular velocity equal to 1/1000 of Earth's
rotation rate. It was introduced by MIT's Instrumentation Laboratories (now
Draper Labs) to measure the performance of
inertial navigation system
An inertial navigation system (INS) is a navigation device that uses motion sensors (accelerometers), rotation sensors ( gyroscopes) and a computer to continuously calculate by dead reckoning the position, the orientation, and the velocity (dir ...
s. One MERU =
or about 0.2625 milliradians/hour.
Energy
Gasoline gallon equivalent
In 2011, the
United States Environmental Protection Agency
The Environmental Protection Agency (EPA) is an independent executive agency of the United States federal government tasked with environmental protection matters. President Richard Nixon proposed the establishment of EPA on July 9, 1970; it ...
introduced the ''gallon gasoline equivalent'' as a unit of energy because their research showed most U.S. citizens do not understand the standard units. The gallon gasoline equivalent is defined as 33.7 kWh,
or about 1.213 joules.
Efficiency / fuel economy can be given as
miles per gallon gasoline equivalent
Miles per gallon gasoline equivalent (MPGe or MPGge) is a measure of the average distance traveled per unit of energy consumed. MPGe is used by the United States Environmental Protection Agency (EPA) to compare energy consumption of alternative ...
.
Tons of TNT equivalent
The energy of various amounts of the explosive
TNT
Trinitrotoluene (), more commonly known as TNT, more specifically 2,4,6-trinitrotoluene, and by its preferred IUPAC name 2-methyl-1,3,5-trinitrobenzene, is a chemical compound with the formula C6H2(NO2)3CH3. TNT is occasionally used as a reagen ...
(kiloton, megaton, gigaton) is often used as a unit of
explosion energy, and sometimes of asteroid impacts and violent explosive volcanic eruptions. One ton of TNT produces 4.184 joules, or (by arbitrary definition) exactly
thermochemical calories (approximately 3.964 BTU). This definition is only loosely based on the actual physical properties of TNT.
Hiroshima bomb and Halifax explosion
![Halifax Explosion blast cloud](https://upload.wikimedia.org/wikipedia/commons/3/37/Halifax_Explosion_blast_cloud.jpg)
The energy released by the
Hiroshima bomb explosion (about 15 kt TNT equivalent, or 6 J) is often used by
geologist
A geologist is a scientist who studies the solid, liquid, and gaseous matter that constitutes Earth and other terrestrial planets, as well as the processes that shape them. Geologists usually study geology, earth science, or geophysics, althoug ...
s as a unit when describing the energy of
earthquake
An earthquake (also known as a quake, tremor or temblor) is the shaking of the surface of the Earth resulting from a sudden release of energy in the Earth's lithosphere that creates seismic waves. Earthquakes can range in intensity, fr ...
s,
volcanic eruption
Several types of volcanic eruptions—during which lava, tephra (ash, lapilli, volcanic bombs and volcanic blocks), and assorted gases are expelled from a volcanic vent or fissure—have been distinguished by volcanologists. These are oft ...
s, and
asteroid impact
An impact event is a collision between astronomical objects causing measurable effects. Impact events have physical consequences and have been found to regularly occur in planetary systems, though the most frequent involve asteroids, comets or me ...
s.
Prior to the detonation of the Hiroshima bomb, the size of the
Halifax Explosion
On the morning of 6 December 1917, the French cargo ship collided with the Norwegian vessel in the waters of Halifax, Nova Scotia, Canada. The ''Mont-Blanc'', laden with high explosives, caught fire and exploded, devastating the Richmond ...
(about 3 kt TNT equivalent, or 1.26 J), was the standard for this type of relative measurement. Each explosion had been the largest known artificial detonation to date.
Quad
A
quad is a unit of energy equal to
BTUs, or approximately 1.055 J (slightly over one exajoule). It is suitably large to quantify energy usage by nations or by the planet as whole using everyday numbers. For example, in 2004, US energy consumption was about 100 Q/year, while demand worldwide was about 400 Q/year.
Foe
A
foe is a unit of energy equal to
joule
The joule ( , ; symbol: J) is the unit of energy in the International System of Units (SI). It is equal to the amount of work done when a force of 1 newton displaces a mass through a distance of 1 metre in the direction of the force applie ...
s (≈9.478
BTU
The British thermal unit (BTU or Btu) is a unit of heat; it is defined as the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit. It is also part of the United States customary units. The modern SI u ...
) that was coined by physicist Gerry Brown of
Stony Brook University. To measure the staggeringly immense amount of energy produced by a
supernova, specialists occasionally use the "foe", an acronym derived from the phrase
en to the power offifty-one ergs, or
erg
The erg is a unit of energy equal to 10−7joules (100 nJ). It originated in the Centimetre–gram–second system of units (CGS). It has the symbol ''erg''. The erg is not an SI unit. Its name is derived from (), a Greek word meaning 'work' o ...
s. This unit of measure is convenient because a supernova typically releases about one foe of observable energy in a very short period of time (which can be measured in seconds).
Other metric-compatible scales
Power: Ton of refrigeration
The rate at which heat is removed by melting of ice in 24 hours is called a ton of refrigeration, or even a ton of cooling. This unit of refrigeration capacity came from the days when large blocks of ice were used for cooling, and is still used to describe the heat-removal capabilities of refrigerators and chillers today. One ton of refrigeration is exactly equal to 12,000 BTU/h, or 3.517 kW.
Luminous flux: watt equivalent
With the phaseout of the
incandescent lamp in the United States and European Union in the early 21st century, manufacturers and sellers of more energy-efficient lamps have compared the visible light output of their lamps to commonly used incandescent lamp sizes with the ''
watt
The watt (symbol: W) is the unit of power or radiant flux in the International System of Units (SI), equal to 1 joule per second or 1 kg⋅m2⋅s−3. It is used to quantify the rate of energy transfer. The watt is named after James ...
equivalent'' or ''watt incandescent replacement'' (usually with a lowercase w as a unit symbol, as opposed to capital W for the actual wattage). 1 watt incandescent replacement corresponds to 15
lumens. Thus, a 72-watt
halogen lamp
A halogen lamp (also called tungsten halogen, quartz-halogen, and quartz iodine lamp) is an incandescent lamp consisting of a tungsten filament sealed in a compact transparent envelope that is filled with a mixture of an inert gas and a small ...
, a 23-watt
compact fluorescent lamp
A compact fluorescent lamp (CFL), also called compact fluorescent light, energy-saving light and compact fluorescent tube, is a fluorescent lamp designed to replace an incandescent light bulb; some types fit into light fixtures designed for inca ...
and a 14-watt
light-emitting diode lamp, all of which emit 1500 lumens of visible light, are all marketed as "100 watt incandescent replacement" (100w).
Flow: Amazon River
The volume of discharge of the
Amazon River sometimes used to describe large volumes of water flow such as ocean currents. The unit is equivalent to 216,000
m3/s.
Flow: Sverdrup
One
Sverdrup
In oceanography, the sverdrup (symbol: Sv) is a non- SI metric unit of volumetric flow rate, with equal to . It is equivalent to the SI derived unit cubic hectometer per second (symbol: hm3/s or hm3⋅s−1): 1 Sv is equal to 1 hm3/s. It is u ...
(Sv) is equal to 1,000,000 cubic metres per second (264,000,000 USgal/s). It is used almost exclusively in
oceanography to measure the volumetric rate of transport of
ocean current
An ocean current is a continuous, directed movement of sea water generated by a number of forces acting upon the water, including wind, the Coriolis effect, breaking waves, cabbeling, and temperature and salinity differences. Depth contours ...
s.
Energy intensity
The
langley (symbol Ly) is used to measure solar radiation or
insolation. It is equal to one thermochemical
calorie per square centimetre (4.184 J/m
2 or ≈3.684 BTU/sq ft) and was named after
Samuel Pierpont Langley
Samuel Pierpont Langley (August 22, 1834 – February 27, 1906) was an American aviation pioneer, astronomer and physicist who invented the bolometer. He was the third secretary of the Smithsonian Institution and a professor of astronomy a ...
. Its symbol should not be confused with that for the light-year, ly.
Kinematic viscosity
One of the few
CGS units to see wider use, one
stokes (symbol S or St) is a unit of
kinematic
Kinematics is a subfield of physics, developed in classical mechanics, that describes the motion of points, bodies (objects), and systems of bodies (groups of objects) without considering the forces that cause them to move. Kinematics, as a fiel ...
viscosity
The viscosity of a fluid is a measure of its resistance to deformation at a given rate. For liquids, it corresponds to the informal concept of "thickness": for example, syrup has a higher viscosity than water.
Viscosity quantifies the inte ...
, defined as 1 cm
2/s, i.e., 10
−4 m
2/s (≈1.08×10
−3 sq ft/s).
Angular velocity
MERU (Milli Earth Rate Unit), an
angular velocity equal to of Earth's rotation rate: 1 MERU = 0.015 degrees/hour ≈ 0.072921 microradian/second. Sometimes used to measure the angular drift rate of an
inertial navigation system
An inertial navigation system (INS) is a navigation device that uses motion sensors (accelerometers), rotation sensors ( gyroscopes) and a computer to continuously calculate by dead reckoning the position, the orientation, and the velocity (dir ...
.
Electromagnetic flux
In
radio astronomy
Radio astronomy is a subfield of astronomy that studies celestial objects at radio frequencies. The first detection of radio waves from an astronomical object was in 1933, when Karl Jansky at Bell Telephone Laboratories reported radiation comin ...
, the unit of
electromagnetic flux is the
jansky
The jansky (symbol Jy, plural ''janskys'') is a non- SI unit of spectral flux density, or spectral irradiance, used especially in radio astronomy. It is equivalent to 10−26 watts per square metre per hertz.
The ''flux density'' or ''monoch ...
(symbol Jy), equivalent to 10
−26 watt
The watt (symbol: W) is the unit of power or radiant flux in the International System of Units (SI), equal to 1 joule per second or 1 kg⋅m2⋅s−3. It is used to quantify the rate of energy transfer. The watt is named after James ...
s per square metre per
hertz
The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that o ...
(= 10
−26 kg/s
2 in base units, about 8.8×10
−31 BTU/ft
2). It is named after the pioneering radio astronomer
Karl Jansky. The brightest natural radio sources have flux densities of the order of one to one hundred jansky.
Metre of water equivalent
A material-dependent unit used in
nuclear and
particle physics
Particle physics or high energy physics is the study of fundamental particles and forces that constitute matter and radiation. The fundamental particles in the universe are classified in the Standard Model as fermions (matter particles) an ...
and engineering to measure the thickness of shielding, for example around a
nuclear reactor
A nuclear reactor is a device used to initiate and control a fission nuclear chain reaction or nuclear fusion reactions. Nuclear reactors are used at nuclear power plants for electricity generation and in nuclear marine propulsion. Heat fr ...
,
particle accelerator
A particle accelerator is a machine that uses electromagnetic fields to propel charged particles to very high speeds and energies, and to contain them in well-defined beams.
Large accelerators are used for fundamental research in particle ...
, or
radiation or particle detector. 1 mwe of a material is the thickness of that material that provides the equivalent shielding of one metre (≈39.4 in) of water.
This unit is commonly used in underground science to express the extent to which the
overburden
In mining, overburden (also called waste or spoil) is the material that lies above an area that lends itself to economical exploitation, such as the rock, soil, and ecosystem that lies above a coal seam or ore body. Overburden is distinct from tai ...
(usually rock) shields an underground space or laboratory from
cosmic ray
Cosmic rays are high-energy particles or clusters of particles (primarily represented by protons or atomic nuclei) that move through space at nearly the speed of light. They originate from the Sun, from outside of the Solar System in our own ...
s. The actual thickness of overburden through which cosmic rays must traverse to reach the underground space varies as a function of direction due to the shape of the overburden, which may be a mountain, or a flat plain, or something more complex like a cliff side. To express the depth of an underground space in mwe (or kmwe for deep sites) as a single number, the convention is to use the depth beneath a flat overburden at
sea level
Mean sea level (MSL, often shortened to sea level) is an average surface level of one or more among Earth's coastal bodies of water from which heights such as elevation may be measured. The global MSL is a type of vertical datuma standardise ...
that gives the same overall cosmic ray
muon flux in the underground location.
Strontium unit: radiation dose
The
strontium unit, formerly known as the Sunshine Unit (symbol S.U.), is a unit of biological contamination by radioactive substances (specifically
strontium-90
Strontium-90 () is a radioactive isotope of strontium produced by nuclear fission, with a half-life of 28.8 years. It undergoes β− decay into yttrium-90, with a decay energy of 0.546 MeV. Strontium-90 has applications in medicine and ...
). It is equal to one
picocurie
The curie (symbol Ci) is a non-International System of Units, SI unit of Radioactive decay, radioactivity originally defined in 1910. According to a notice in ''Nature (magazine), Nature'' at the time, it was to be named in honour of Pierre Curie ...
of Sr-90 per
gram
The gram (originally gramme; SI unit symbol g) is a unit of mass in the International System of Units (SI) equal to one one thousandth of a kilogram.
Originally defined as of 1795 as "the absolute weight of a volume of pure water equal to th ...
of body
calcium
Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar t ...
. Since about 2% of the human body mass is calcium, and Sr-90 has a
half-life
Half-life (symbol ) is the time required for a quantity (of substance) to reduce to half of its initial value. The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay or how long stable at ...
of 28.78 years, releasing 6.697+2.282
MeV
In physics, an electronvolt (symbol eV, also written electron-volt and electron volt) is the measure of an amount of kinetic energy gained by a single electron accelerating from rest through an electric potential difference of one volt in vacu ...
per disintegration, this works out to about 1.065
gray
Grey (more common in British English) or gray (more common in American English) is an intermediate color between black and white. It is a neutral or achromatic color, meaning literally that it is "without color", because it can be composed o ...
s per second. The permissible body burden was established at 1,000 S.U.
Banana equivalent dose
![Bananen Frucht](https://upload.wikimedia.org/wikipedia/commons/4/4e/Bananen_Frucht.jpg)
Bananas, like most organic material, naturally contain a certain amount of radioactive isotopes—even in the absence of any artificial pollution or contamination. The
banana equivalent dose, defined as the additional dose a person will absorb from eating one banana, expresses the severity of exposure to radiation, such as resulting from nuclear weapons or medical procedures, in terms that would make sense to most people. This is approximately 78 nano
sievert
The sievert (symbol: SvNot be confused with the sverdrup or the svedberg, two non-SI units that sometimes use the same symbol.) is a unit in the International System of Units (SI) intended to represent the stochastic health risk of ionizing rad ...
s – in informal publications one often sees this estimate rounded up to 0.1 μSv.
Flight-time equivalent dose
Natural background radiation typically increases with altitude above the earth’s surface. Utilizing this phenomenon, dose resulting from radiological exposures can be expressed in units of flight-time.
Flight-time equivalent dose is defined as the time spent in an aircraft at cruising altitude required to receive a radiological dose approximately equivalent to a radiological exposure such as a medical
x-ray
An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 picometers to 10 nanometers, corresponding to frequencies in the range 30&nb ...
. One hour of flight-time is approximately equivalent to a dose of 0.004 milli
sievert
The sievert (symbol: SvNot be confused with the sverdrup or the svedberg, two non-SI units that sometimes use the same symbol.) is a unit in the International System of Units (SI) intended to represent the stochastic health risk of ionizing rad ...
s.
Molar mass of cellulose
In the
pulp and paper industry,
molar mass
In chemistry, the molar mass of a chemical compound is defined as the mass of a sample of that compound divided by the amount of substance which is the number of moles in that sample, measured in moles. The molar mass is a bulk, not molecular, ...
is traditionally measured with a method where the
intrinsic viscosity Intrinsic viscosity \left \eta \right/math> is a measure of a solute's contribution to the viscosity \eta of a solution. It should not be confused with inherent viscosity, which is the ratio of the natural logarithm of the relative viscosity to th ...
(dL/g) of the pulp sample is measured in cupriethylenediamine (Cuen). The intrinsic viscosity
is related to the weight-average molar mass (in
dalton
Dalton may refer to:
Science
* Dalton (crater), a lunar crater
* Dalton (program), chemistry software
* Dalton (unit) (Da), the atomic mass unit
* John Dalton, chemist, physicist and meteorologist
Entertainment
* Dalton (Buffyverse), minor ch ...
s) by the
Mark-Houwink equation:
= 0.070 M
w0.70. However, it is typical to cite
values directly in dL/g, as the "viscosity" of the cellulose, confusingly as it is not a viscosity.
Iodine, bromine and kappa number
In measuring unsaturation in fatty acids, the traditional method is the
iodine number
Iodine is a chemical element with the symbol I and atomic number 53. The heaviest of the stable halogens, it exists as a semi-lustrous, non-metallic solid at standard conditions that melts to form a deep violet liquid at , and boils to a vio ...
. Iodine adds stoichiometrically to double bonds, so their amount is reported in grams of iodine spent per 100 grams of oil. The standard unit is a dimensionless stoichiometry ratio of moles double bonds to moles fatty acid. A similar quantity,
bromine number
In chemistry, the bromine number is the amount of bromine () in grams absorbed by of a sample. The number indicates the degree of unsaturation.
The bromine number is useful as a measure of aliphatic unsaturation in gasoline samples. The Calif ...
, is used in gasoline analysis.
In pulp and paper industry, a similar
kappa number
The Kappa number is an indication of the residual lignin content or bleachability of wood pulp by a standardized analysis method.
Measuring method
The Kappa number is determined by ISO 302:2004. ISO 302 is applicable to all kinds of chemical an ...
is used to measure how much
bleaching
Bleach is the generic name for any chemical product that is used industrially or domestically to remove color (whitening) from a fabric or fiber or to clean or to remove stains in a process called bleaching. It often refers specifically, to ...
a pulp requires.
Potassium permanganate
Potassium permanganate is an inorganic compound with the chemical formula KMnO4. It is a purplish-black crystalline salt, that dissolves in water as K+ and , an intensely pink to purple solution.
Potassium permanganate is widely used in the c ...
is added to react with the unsaturated compounds (lignin and uronic acids) in the pulp and back-titrated. Originally with
chlorine bleaching the required quantity of
chlorine
Chlorine is a chemical element with the symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between them. Chlorine i ...
could be then calculated, although modern methods use multiple stages. Since the oxidizable compounds are not exclusively lignin and the partially pulped lignin does not have a single stoichiometry, the relation between the kappa number and the precise
amount
Quantity or amount is a property that can exist as a multitude or magnitude, which illustrate discontinuity and continuity. Quantities can be compared in terms of "more", "less", or "equal", or by assigning a numerical value multiple of a unit ...
of lignin is inexact.
Temperature: Gas Mark
Gas Mark is a temperature scale, predominantly found on British
ovens, that scales
linearly
Linearity is the property of a mathematical relationship (''function'') that can be graphically represented as a straight line. Linearity is closely related to '' proportionality''. Examples in physics include rectilinear motion, the linear r ...
with temperature above 135 °C (Gas Mark 1) and scales with the
log
Log most often refers to:
* Trunk (botany), the stem and main wooden axis of a tree, called logs when cut
** Logging, cutting down trees for logs
** Firewood, logs used for fuel
** Lumber or timber, converted from wood logs
* Logarithm, in mathe ...
of Celsius below 135 °C.
Demography and epidemiology
Demography
Demography () is the statistical study of populations, especially human beings.
Demographic analysis examines and measures the dimensions and dynamics of populations; it can cover whole societies or groups defined by criteria such as edu ...
and quantitative
epidemiology
Epidemiology is the study and analysis of the distribution (who, when, and where), patterns and determinants of health and disease conditions in a defined population.
It is a cornerstone of public health, and shapes policy decisions and evide ...
are
statistical fields that deal with
counts
Count (feminine: countess) is a historical title of nobility in certain European countries, varying in relative status, generally of middling rank in the hierarchy of nobility. Pine, L. G. ''Titles: How the King Became His Majesty''. New York: ...
or proportions of people, or rates of change in these.
Counts
Count (feminine: countess) is a historical title of nobility in certain European countries, varying in relative status, generally of middling rank in the hierarchy of nobility. Pine, L. G. ''Titles: How the King Became His Majesty''. New York: ...
and proportions are technically
dimensionless
A dimensionless quantity (also known as a bare quantity, pure quantity, or scalar quantity as well as quantity of dimension one) is a quantity to which no physical dimension is assigned, with a corresponding SI unit of measurement of one (or 1) ...
, and so have no
units of measurement
A unit of measurement is a definite magnitude of a quantity, defined and adopted by convention or by law, that is used as a standard for measurement of the same kind of quantity. Any other quantity of that kind can be expressed as a multi ...
, although identifiers such as "people", "births", "infections" and the like are used for clarity. Rates of change are
counts per unit of time and strictly have inverse time dimensions (per unit of time). In
demography
Demography () is the statistical study of populations, especially human beings.
Demographic analysis examines and measures the dimensions and dynamics of populations; it can cover whole societies or groups defined by criteria such as edu ...
and epidemiology expressions such as
"deaths per year" are used to clarify what is being measured.
Prevalence
In epidemiology, prevalence is the proportion of a particular population found to be affected by a medical condition (typically a disease or a risk factor such as smoking or seatbelt use) at a specific time. It is derived by comparing the number o ...
, a common measure in
epidemiology
Epidemiology is the study and analysis of the distribution (who, when, and where), patterns and determinants of health and disease conditions in a defined population.
It is a cornerstone of public health, and shapes policy decisions and evide ...
is strictly a type of
denominator data
In epidemiology, data or facts about a population is called denominator data. Denominator data are independent of any specific disease or condition. This name is given because in mathematical models of disease, disease-specific data such as the ...
, a dimensionless ratio or proportion.
Prevalence
In epidemiology, prevalence is the proportion of a particular population found to be affected by a medical condition (typically a disease or a risk factor such as smoking or seatbelt use) at a specific time. It is derived by comparing the number o ...
may be expressed as a fraction, a percentage or as the number of cases per 1,000, 10,000, or 100,000 in the population of interest.
Micromort
A micromort is a unit of
risk
In simple terms, risk is the possibility of something bad happening. Risk involves uncertainty about the effects/implications of an activity with respect to something that humans value (such as health, well-being, wealth, property or the environm ...
measuring a one-in-a-million
probability
Probability is the branch of mathematics concerning numerical descriptions of how likely an event is to occur, or how likely it is that a proposition is true. The probability of an event is a number between 0 and 1, where, roughly speakin ...
of
death
Death is the irreversible cessation of all biological functions that sustain an organism. For organisms with a brain, death can also be defined as the irreversible cessation of functioning of the whole brain, including brainstem, and brain ...
(from
micro-
''Micro'' (Greek letter μ ( U+03BC) or the legacy symbol µ (U+00B5)) is a unit prefix in the metric system denoting a factor of 10−6 (one millionth). Confirmed in 1960, the prefix comes from the Greek ('), meaning "small".
The symbol for ...
and
mortality). Micromorts can be used to measure riskiness of various day-to-day activities. A microprobability is a one-in-a million chance of some event; thus a micromort is the microprobability of death. For example, smoking 1.4 cigarettes increases one's death risk by one micromort, as does traveling by car.
Numbers of people: Stadium capacities
![AFL Grand Final 2010 on the Melbourne Cricket Ground](https://upload.wikimedia.org/wikipedia/commons/4/41/AFL_Grand_Final_2010_on_the_Melbourne_Cricket_Ground.jpg)
The large numbers of people involved in
demography
Demography () is the statistical study of populations, especially human beings.
Demographic analysis examines and measures the dimensions and dynamics of populations; it can cover whole societies or groups defined by criteria such as edu ...
are often difficult to comprehend. A useful visualisation tool is the audience capacity of large sports stadiums (often about 100,000). Often the capacity of the largest stadium in a region serves as a unit for a large number of people. For example, Uruguay's
Estadio Centenario
Estadio Centenario is a stadium in the Parque Batlle of Montevideo, Uruguay, used primarily for football. The stadium was built between 1929 and 1930 to host the inaugural 1930 FIFA World Cup, as well as to commemorate the centenary of Ur ...
is often used in
Uruguay
Uruguay (; ), officially the Oriental Republic of Uruguay ( es, República Oriental del Uruguay), is a country in South America. It shares borders with Argentina to its west and southwest and Brazil to its north and northeast; while bordering ...
, while in parts of the United States,
Michigan Stadium
Michigan Stadium, nicknamed "The Big House," is the football stadium for the University of Michigan in Ann Arbor, Michigan. It is the largest stadium in the United States and the Western Hemisphere, the third largest stadium in the world, and the ...
is used in this manner. In Australia, the capacity of the
Melbourne Cricket Ground (about 100,000) is often cited in this manner. Hence the
Melbourne Cricket Ground serves as both a measure of people and a
unit of volume
A unit of volume is a unit of measurement for measuring volume or capacity, the extent of an object or space in three dimensions. Units of capacity may be used to specify the volume of fluids or bulk goods, for example water, rice, sugar, grain or ...
.
Computer and information science
The growth of computing has necessitated the creation of many new units, several of which are based on unusual foundations.
Data volume
![Print vs](https://upload.wikimedia.org/wikipedia/commons/f/f0/Print_vs._bytes.jpg)
Volume or capacity of data is often compared to works of literature or large collections of writing. Popular units include the Bible, the Encyclopaedia Britannica, phone books,
the complete works of Shakespeare, and the
Library of Congress
The Library of Congress (LOC) is the research library that officially serves the United States Congress and is the ''de facto'' national library of the United States. It is the oldest federal cultural institution in the country. The library ...
.
When the
Compact Disc
The compact disc (CD) is a digital optical disc data storage format that was co-developed by Philips and Sony to store and play digital audio recordings. In August 1982, the first compact disc was manufactured. It was then released in Oc ...
began to be used as a
data storage device as the
CD-ROM, journalists often described the disc capacity (650
megabytes) by using the number of Christian
Bible
The Bible (from Koine Greek , , 'the books') is a collection of religious texts or scriptures that are held to be sacred in Christianity, Judaism, Samaritanism, and many other religions. The Bible is an anthologya compilation of texts ...
s that can be stored. The
King James Version of the Bible in uncompressed plain 8-bit text contains about 4.5 million characters, so a
CD-ROM can store about 150
Bible
The Bible (from Koine Greek , , 'the books') is a collection of religious texts or scriptures that are held to be sacred in Christianity, Judaism, Samaritanism, and many other religions. The Bible is an anthologya compilation of texts ...
s.
The print version of the ''
Encyclopædia Britannica
The (Latin for "British Encyclopædia") is a general knowledge English-language encyclopaedia. It is published by Encyclopædia Britannica, Inc.; the company has existed since the 18th century, although it has changed ownership various t ...
'' is another common data volume metric. It contains approximately 300 million characters, so two copies would fit onto a
CD-ROM and still have 50 megabytes (or about 11 bibles) left over.
The term ''Library of Congress'' is often used. It refers to the US
Library of Congress
The Library of Congress (LOC) is the research library that officially serves the United States Congress and is the ''de facto'' national library of the United States. It is the oldest federal cultural institution in the country. The library ...
. Information researchers have estimated that the entire print collections of the Library of Congress represent roughly 10
terabyte
The byte is a unit of digital information that most commonly consists of eight bits. Historically, the byte was the number of bits used to encode a single character of text in a computer and for this reason it is the smallest addressable uni ...
s of uncompressed
textual data.
Nibble
A measure of quantity of data or information, the "
nibble" (sometimes spelled "nybble" or "nybl") is normally equal to 4 bits, or one half of the common 8-bit byte. The nibble is used to describe the amount of memory used to store a digit of a number stored in
binary-coded decimal format, or to represent a single hexadecimal digit. Less commonly, 'nibble' may be used for any contiguous portion of a byte of specified length, e.g. "6-bit nibble"; this usage is most likely to be encountered in connection with a hardware architecture in which the word length is not a multiple of 8, such as older 36-bit minicomputers.
FLOPS
In
computing
Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It includes the study and experimentation of algorithmic processes, and development of both hardware and software. Computing has scientific, ...
, FLOPS (''FL''oating point ''O''perations ''P''er ''S''econd) is a measure of a computer's computing power. It is also common to see measurements of kilo, mega, giga, and teraFLOPS.
It is also used to compare the performance of computers in practice.
BogoMips
A measure to determine the
CPU speed. It was invented by
Linus Torvalds
Linus Benedict Torvalds ( , ; born 28 December 1969) is a Finnish software engineer who is the creator and, historically, the lead developer of the Linux kernel, used by Linux distributions and other operating systems such as Android. He also ...
and is nowadays present on every
Linux
Linux ( or ) is a family of open-source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically packaged as a Linux distribution, w ...
operating system. However, it is not a meaningful measure to assess the actual
CPU performance.
KLOC
A computer programming expression, the
K-LOC or KLOC, pronounced ''kay-lok'', standing for "kilo-
lines of code
Source lines of code (SLOC), also known as lines of code (LOC), is a software metric used to measure the size of a computer program by counting the number of lines in the text of the program's source code. SLOC is typically used to predict the am ...
", i.e., thousand lines of code. The unit was used, especially by
IBM managers, to express the amount of work required to develop a piece of software. Given that estimates of 20 lines of functional code per day per programmer were often used, it is apparent that 1 K-LOC could take one programmer as long as 50 working days, or 10 working weeks. This measure is no longer in widespread use because different computer languages require different numbers of lines to achieve the same result (occasionally the measure "assembly equivalent lines of code" is used, with appropriate conversion factors from the language actually used to assembly language).
Error rates in programming are also measured in "Errors per K-LOC", which is called the ''defect density''. NASA's
SATC is one of the few organizations to claim zero defects in a large (>500K-LOC) project, for the space shuttle software.
An alternative measurement was defined by
Pegasus Mail
Pegasus Mail is a proprietary email client developed by David Harris (who also develops the Mercury Mail Transport System). It was originally released in 1990 for internal and external mail on NetWare networks with MS-DOS and later Apple Macint ...
author
David Harris: the "WaP" is equivalent to 71,500 lines of program code, because that number of lines is the length of one edition of
Leo Tolstoy
Count Lev Nikolayevich TolstoyTolstoy pronounced his first name as , which corresponds to the romanization ''Lyov''. () (; russian: link=no, Лев Николаевич Толстой,In Tolstoy's day, his name was written as in pre-refor ...
's ''
War and Peace
''War and Peace'' (russian: Война и мир, translit=Voyna i mir; pre-reform Russian: ; ) is a literary work by the Russian author Leo Tolstoy that mixes fictional narrative with chapters on history and philosophy. It was first published ...
''.
Ticks
The "tick" is the amount of time between timer
interrupt
In digital computers, an interrupt (sometimes referred to as a trap) is a request for the processor to ''interrupt'' currently executing code (when permitted), so that the event can be processed in a timely manner. If the request is accepted, ...
s generated by the timer circuit of a CPU. The amount of time is processor-dependent.
Other
Centipawn
Chess
Chess is a board game for two players, called White and Black, each controlling an army of chess pieces in their color, with the objective to checkmate the opponent's king. It is sometimes called international chess or Western chess to dist ...
software frequently uses centipawns internally or externally as a unit measuring how strong each player's situation position is, and hence also by how much one player is beating the other, and how strong a possible move is. 100 centipawns =
the value of 1 pawn – more specifically, something like the average value of the pawns at the start of the game, as the actual value of pawns depends on their position. Loss of a pawn will therefore typically lose that player 100 centipawns. The centipawn is often used for comparing possible moves, as in a given position, chess software will often rate the better of two moves within a few centipawns of each other.
Garn
The garn is NASA's unit of measure for symptoms resulting from
space adaptation syndrome, the response of the human body to weightlessness in space, named after US Senator
Jake Garn
Edwin Jacob "Jake" Garn (born October 12, 1932) is an American politician and member of the Republican Party who served as a United States senator representing Utah from 1974 to 1993. Garn became the first sitting member of Congress to fly in sp ...
, who became exceptionally spacesick during an orbital flight in 1985. If an astronaut is completely incapacitated by space adaptation syndrome, he or she is under the effect of one garn of symptoms.
Mother Cow Index
Formerly used in real estate transactions in the American Southwest, it was the number of pregnant cows an acre of a given plot of land could support. It acted as a proxy for the agricultural quality, natural resource availability, and arability of a parcel of land.
Nines
Numbers very close to, but below one are often expressed in "
nines" (N – not to be confused with the unit
newton), that is in the number of nines following the decimal separator in writing the number in question. For example, "three nines" or "3N" indicates 0.999 or 99.9%, "four nines five" or "4N5" is the expression for the number 0.99995 or 99.995%.
Typical areas of usage are:
*The
reliability
Reliability, reliable, or unreliable may refer to:
Science, technology, and mathematics Computing
* Data reliability (disambiguation), a property of some disk arrays in computer storage
* High availability
* Reliability (computer networking), a ...
of computer systems, that is the ratio of
uptime
Uptime is a measure of system reliability, expressed as the percentage of time a machine, typically a computer, has been working and available. Uptime is the opposite of downtime.
It is often used as a measure of computer operating system reliab ...
to the sum of
uptime
Uptime is a measure of system reliability, expressed as the percentage of time a machine, typically a computer, has been working and available. Uptime is the opposite of downtime.
It is often used as a measure of computer operating system reliab ...
and
downtime
The term downtime is used to refer to periods when a system is unavailable.
The unavailability is the proportion of a time-span that a system is unavailable or offline.
This is usually a result of the system failing to function because of an u ...
. "Five nines" reliability in a continuously operated system means an average
downtime
The term downtime is used to refer to periods when a system is unavailable.
The unavailability is the proportion of a time-span that a system is unavailable or offline.
This is usually a result of the system failing to function because of an u ...
of no more than approximately five minutes per year (there is no relationship between the number of nines and minutes per year, it is pure coincidence that "five nines" relates to five minutes per year.) (See
high availability
High availability (HA) is a characteristic of a system which aims to ensure an agreed level of operational performance, usually uptime, for a higher than normal period.
Modernization has resulted in an increased reliance on these systems. F ...
for a chart.)
*The
purity
Purity may refer to:
Books
* ''Pureza'' (novel), a 1937 Brazilian novel by José Lins do Rego
* ''Purity'' (novel), a 2015 novel by Jonathan Franzen
** ''Purity'' (TV series), a TV series based on the novel
*''Purity'', a 2012 novel by Jackson P ...
of materials, such as gases and metals.
Pain
![OuchFlintGoodrichShot1941](https://upload.wikimedia.org/wikipedia/commons/c/ca/OuchFlintGoodrichShot1941.jpg)
The dol (from the
Latin
Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...
word for pain, ''dolor'') is a
unit of measurement
A unit of measurement is a definite magnitude of a quantity, defined and adopted by convention or by law, that is used as a standard for measurement of the same kind of quantity. Any other quantity of that kind can be expressed as a multi ...
for
pain.
James D. Hardy,
Herbert G. Wolff, and
Helen Goodell of
Cornell University
Cornell University is a private statutory land-grant research university based in Ithaca, New York. It is a member of the Ivy League. Founded in 1865 by Ezra Cornell and Andrew Dickson White, Cornell was founded with the intention to tea ...
proposed the unit based on their studies of pain during the 1940s and 1950s. They defined one dol to equal to "just noticeable differences" (
jnd's) in pain. The unit never came into widespread use and other methods are now used to assess the level of pain experienced by patients.
The Schmidt sting pain index and Starr sting pain index are
pain scale
A pain scale measures a patient's pain intensity or other features. Pain scales are a common communication tool in medical contexts, and are used in a variety of medical settings. Pain scales are a necessity to assist with better assessment of pai ...
s rating the relative pain caused by different
hymenopteran stings. Schmidt has refined his
Schmidt Sting Pain Index
The Schmidt sting pain index is a pain scale rating the relative pain caused by different hymenopteran stings. It is mainly the work of Justin O. Schmidt (born 1947), an entomologist at the Carl Hayden Bee Research Center in Arizona, United Sta ...
(scaled from 1 to 4) with extensive anecdotal experience, culminating in a paper published in 1990 which classifies the stings of 78 species and 41 genera of Hymenoptera. The
Starr sting pain scale uses the same 1-to-4 scaling.
Pepper heat
ASTA pungency unit
The ASTA (
American Spice Trade Association
The American Spice Trade Association (ASTA) is an American trade association for companies importing, processing and distributing food spices. It was founded in New York City in 1907 by 55 "founding fathers". It was decided that ASTA membership wo ...
)
pungency
Pungency () refers to the taste of food commonly referred to as spiciness, hotness or heat, found in foods such as chili peppers. Highly pungent tastes may be experienced as unpleasant. The term piquancy () is sometimes applied to foods with a l ...
unit is based on a scientific method of measuring chili pepper "heat". The technique utilizes
high-performance liquid chromatography
High-performance liquid chromatography (HPLC), formerly referred to as high-pressure liquid chromatography, is a technique in analytical chemistry used to separate, identify, and quantify each component in a mixture. It relies on pumps to pa ...
to identify and measure the concentrations of the various compounds that produce a heat sensation. Scoville units are roughly the size of pungency units while measuring
capsaicin
Capsaicin (8-methyl-''N''-vanillyl-6-nonenamide) ( or ) is an active component of chili peppers, which are plants belonging to the genus ''Capsicum''. It is a chemical irritant for mammals, including humans, and produces a sensation of burnin ...
, so a rough conversion is to multiply pungency by 15 to obtain Scoville heat units.
[ — "Interlab variation or the original Scoville scalecould be as high as ±50%. However, labs that run these procedures could generate reasonably repeatable results."]
Scoville heat unit
![Madame Jeanette and other chillies](https://upload.wikimedia.org/wikipedia/commons/5/50/Madame_Jeanette_and_other_chillies.jpg)
The
Scoville scale
The Scoville scale is a measurement of the pungency (spiciness or "heat") of chili peppers, as recorded in Scoville heat units (SHU), based on the concentration of capsaicinoids, among which capsaicin is the predominant component.
The scale i ...
is a measure of the hotness of a
chili pepper
Chili peppers (also chile, chile pepper, chilli pepper, or chilli), from Nahuatl '' chīlli'' (), are varieties of the berry-fruit of plants from the genus ''Capsicum'', which are members of the nightshade family Solanaceae, cultivated for ...
. It is the degree of dilution in sugar water of a specific chili pepper extract when a panel of 5 tasters can no longer detect its "heat".
Pure
capsaicin
Capsaicin (8-methyl-''N''-vanillyl-6-nonenamide) ( or ) is an active component of chili peppers, which are plants belonging to the genus ''Capsicum''. It is a chemical irritant for mammals, including humans, and produces a sensation of burnin ...
(the chemical responsible for the "heat") has 16 million Scoville heat units.
Proof: alcohol concentration
![Bacardi 151 bottle](https://upload.wikimedia.org/wikipedia/commons/8/8e/Bacardi_151_bottle.jpg)
Up to the 20th century, alcoholic spirits were assessed in the UK by mixing with gunpowder and testing the mixture to see whether it would still burn; spirit that just passed the test was said to be at 100°
proof. The UK now uses percentage
alcohol by volume at 20 °C (68 °F), where spirit at 100° proof is approximately 57.15% ABV; the US uses a "proof number" of twice the ABV at 60 °F (15.5 °C).
Savart
The
Savart
The savart is a unit of measurement for musical pitch intervals (). One savart is equal to one thousandth of a decade ( 10/1: 3,986.313714 cents): 3.9863 cents. Musically, in just intonation, the interval of a decade is precisely a just major ...
is an 18th-century unit for measuring the frequency ratio of two sounds. It is equal to of a
decade
A decade () is a period of ten years. Decades may describe any ten-year period, such as those of a person's life, or refer to specific groupings of calendar years.
Usage
Any period of ten years is a "decade". For example, the statement that "du ...
(not to be confused with the time period equal to 10 years). The
cent is preferred for musical use.
Telecommunications traffic volume
The erlang, named after A. K. Erlang, as a
dimensionless unit
A dimensionless quantity (also known as a bare quantity, pure quantity, or scalar quantity as well as quantity of dimension one) is a quantity to which no physical dimension is assigned, with a corresponding SI unit of measurement of one (or 1) ...
is used in
telephony
Telephony ( ) is the field of technology involving the development, application, and deployment of telecommunication services for the purpose of electronic transmission of voice, fax, or data, between distant parties. The history of telephony is i ...
as a statistical measure of the offered intensity of
telecommunication
Telecommunication is the transmission of information by various types of technologies over wire, radio, optical, or other electromagnetic systems. It has its origin in the desire of humans for communication over a distance greater than that fe ...
s
traffic
Traffic comprises pedestrians, vehicles, ridden or herded animals, trains, and other conveyances that use public ways (roads) for travel and transportation.
Traffic laws govern and regulate traffic, while rules of the road include traffi ...
on a group of resources. Traffic of one erlang refers to a single
resource
Resource refers to all the materials available in our environment which are technologically accessible, economically feasible and culturally sustainable and help us to satisfy our needs and wants. Resources can broadly be classified upon their ...
being in continuous use, or two
channels being at fifty percent use, and so on,
pro rata
''Pro rata'' is an adverb or adjective meaning in equal portions or in proportion. The term is used in many legal and economic contexts. The hyphenated spelling ''pro-rata'' for the adjective form is common, as recommended for adjectives by some E ...
. Much telecommunications management and forecasting software uses this.
X-ray intensity
The crab is defined as the intensity of X-rays emitted from the
Crab Nebula at a given photon energy up to 30 kilo
electronvolts
In physics, an electronvolt (symbol eV, also written electron-volt and electron volt) is the measure of an amount of kinetic energy gained by a single electron accelerating from rest through an electric potential difference of one volt in vacuum ...
. The Crab Nebula is often used for calibration of X-ray telescopes. For measuring the X-ray intensity of a less energetic source, the milliCrab (mCrab) may be used.
One crab is approximately 24 pW/m
2.
See also
*
Conversion of units
Conversion of units is the conversion between different units of measurement for the same quantity, typically through multiplicative conversion factors which change the measured quantity value without changing its effects.
Overview
The process ...
*
GNU Units
GNU Units is a cross-platform computer program for conversion of units of quantities. It has a database of measurement units, including esoteric and historical units. This for instance allows conversion of velocities specified in furlongs per ...
, a unit conversion program, which supports many uncommon units
*
Hair's breadth
A hair's breadth, or the width of human hair, is used as an informal unit of a very short length. It connotes "a very small margin" or the narrowest degree in many contexts.
Definitions
This measurement is not precise because human hair varie ...
*
History of measurement
*
List of humorous units of measurement
Many people have made use of, or invented, units of measurement intended primarily for their humor
Humour (Commonwealth English) or humor (American English) is the tendency of experiences to provoke laughter and provide amusement. The ...
*
List of obsolete units of measurement
This is a list of obsolete units of measurement, organized by type. These units of measurement are typically no longer used, though some may be in limited use in various regions. For units of measurement that are unusual but not necessarily obsolet ...
*
Muggeseggele
*
Unit of measurement
A unit of measurement is a definite magnitude of a quantity, defined and adopted by convention or by law, that is used as a standard for measurement of the same kind of quantity. Any other quantity of that kind can be expressed as a multi ...
References
Bibliography
*
*
{{DEFAULTSORT:List of Unusual Units of Measurement
*
Unusual units of measurement
Unusual units of measurement
Measurement