A system of measurement is a collection of

units of measurement A unit of measurement is a definite magnitude (mathematics), 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 ...

and rules relating them to each other. Systems of measurement have historically been important, regulated and defined for the purposes of

science Science is a systematic endeavor that builds and organizes knowledge in the form of testable explanations and predictions about the universe. Science may be as old as the human species, and some of the earliest archeological evidence for ...

and

commerce Commerce is the large-scale organized system of activities, functions, procedures and institutions directly and indirectly related to the exchange (buying and selling) of goods and services among two or more parties within local, regional, nation ...

. Systems of measurement in use include the

International System of Units The International System of Units, known by the international abbreviation SI in all languages and sometimes pleonastically as the SI system, is the modern form of the metric system and the world's most widely used system of measurement. E ...

or (the modern form of the

metric system The metric system is a system of measurement that succeeded the Decimal, decimalised system based on the metre that had been introduced in French Revolution, France in the 1790s. The historical development of these systems culminated in the d ...

), the

British imperial system 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 thro ...

, and the

United States customary system United States customary units form a system of Units of measurement, measurement units commonly used in the United States and Territories of the United States, U.S. territories since being standardized and adopted in 1832. The United States cust ...

History

The

French Revolution The French Revolution ( ) was a period of radical political and societal change in France that began with the Estates General of 1789 and ended with the formation of the French Consulate in November 1799. Many of its ideas are considere ...

gave rise to the

, and this has spread around the world, replacing most customary units of measure. In most systems,

length Length is a measure of distance. In the International System of Quantities, length is a quantity with dimension distance. In most systems of measurement a base unit for length is chosen, from which all other units are derived. In the Interna ...

(distance),

mass Mass is an intrinsic property of a body. It was traditionally believed to be related to the quantity of matter in a physical body, until the discovery of the atom and particle physics. It was found that different atoms and different elementar ...

, and

time Time is the continued sequence of existence and events that occurs in an apparently irreversible succession from the past, through the present, into the future. It is a component quantity of various measurements used to sequence events, to ...

are ''base quantities''. Later science developments showed that an electromagnetic quantity such as

electric charge Electric charge is the physical property of matter that causes charged matter to experience a force when placed in an electromagnetic field. Electric charge can be ''positive'' or ''negative'' (commonly carried by protons and electrons respe ...

or electric current could be added to extend the set of base quantities.

Gaussian units Gaussian units constitute a metric system of physical units. This system is the most common of the several electromagnetic unit systems based on cgs (centimetre–gram–second) units. It is also called the Gaussian unit system, Gaussian-cgs uni ...

have only length, mass, and time as base quantities, with no separate electromagnetic dimension. Other quantities, such as

power Power most often refers to: * Power (physics), meaning "rate of doing work" ** Engine power, the power put out by an engine ** Electric power * Power (social and political), the ability to influence people or events ** Abusive power Power may a ...

and

speed In everyday use and in kinematics, the speed (commonly referred to as ''v'') of an object is the magnitude of the change of its position over time or the magnitude of the change of its position per unit of time; it is thus a scalar quanti ...

, are derived from the base set: for example, speed is distance per unit time. Historically a wide range of units was used for the same type of quantity: in different contexts, length was measured in

inch Measuring tape with inches The inch (symbol: in or ″) is a unit of length in the British imperial and the United States customary systems of measurement. It is equal to yard or of a foot. Derived from the Roman uncia ("twelfth") ...

es,

feet The foot ( : feet) is an anatomical structure found in many vertebrates. It is the terminal portion of a limb which bears weight and allows locomotion. In many animals with feet, the foot is a separate organ at the terminal part of the leg made ...

yards The yard (symbol: yd) is an English unit of length in both the British imperial and US customary systems of measurement equalling 3 feet or 36 inches. Since 1959 it has been by international agreement standardized as exactly 0.914 ...

fathom A fathom is a unit of length in the imperial and the U.S. customary systems equal to , used especially for measuring the depth of water. The fathom is neither an International Standard (SI) unit, nor an internationally-accepted non-SI unit. Hi ...

s, rods,

chains A chain is a serial assembly of connected pieces, called links, typically made of metal, with an overall character similar to that of a rope in that it is flexible and curved in compression but linear, rigid, and load-bearing in tension. A c ...

furlong A furlong is a measure of distance in imperial units and United States customary units equal to one eighth of a mile, equivalent to 660 feet, 220 yards, 40 rods, 10 chains or approximately 201 metres. It is now mostly confined to use in hors ...

mile The mile, sometimes the international mile or statute mile to distinguish it from other miles, is a British imperial unit and United States customary unit of distance; both are based on the older English unit of length equal to 5,280 English ...

nautical mile A nautical mile is a unit of length used in air, marine, and space navigation, and for the definition of territorial waters. Historically, it was defined as the meridian arc length corresponding to one minute ( of a degree) of latitude. Today ...

stadia Stadia may refer to: * One of the plurals of stadium, along with "stadiums" * The plural of stadion, an ancient Greek unit of distance, which equals to 600 Greek feet (''podes''). * Stadia (Caria), a town of ancient Caria, now in Turkey * Stadi ...

, leagues, with conversion factors that were not powers of ten. The preference for a more universal and consistent system only gradually spread with the growth of international trade and science. Changing a measurement system has costs in the near term, which results in resistance to such a change. The substantial benefit of conversion to a more rational and internationally consistent system of measurement has been recognized and promoted by scientists, engineers and politicians, and has resulted in most of the world adopting a commonly agreed metric system. In antiquity, ''systems of measurement'' were defined locally: the different units might be defined independently according to the length of a king's thumb or the size of his foot, the length of stride, the length of arm, or maybe the weight of water in a keg of specific size, perhaps itself defined in ''hands'' and ''knuckles''. The unifying characteristic is that there was some definition based on some standard. Eventually ''

cubit The cubit is an ancient unit of length based on the distance from the elbow to the tip of the middle finger. It was primarily associated with the Sumerians, Egyptians, and Israelites. The term ''cubit'' is found in the Bible regarding No ...

s'' and '' strides'' gave way to "customary units" to meet the needs of merchants and scientists. In the metric system and other recent systems, underlying relationships between quantities, as expressed by formulae of physics such as

Newton's laws of motion Newton's laws of motion are three basic laws of classical mechanics that describe the relationship between the motion of an object and the forces acting on it. These laws can be paraphrased as follows: # A body remains at rest, or in moti ...

, is used to select a small number of base quantities for which a unit is defined for each, from which all other units may be derived. Secondary units (multiples and submultiples) are derived from these base and derived units by multiplying by powers of ten, so for example where the unit of length is the

metre The metre (British spelling) or meter (American spelling; see spelling differences) (from the French unit , from the Greek noun , "measure"), symbol m, is the primary unit of length in the International System of Units (SI), though its pref ...

; a distance of 1 m is 1,000 millimetres, or 0.001 kilometres.

Current practice

Metrication is complete or nearly complete in almost all countries.

US customary units United States customary units form a system of measurement units commonly used in the United States and U.S. territories since being standardized and adopted in 1832. The United States customary system (USCS or USC) developed from English uni ...

are heavily used in the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...

and to some degree in

Liberia Liberia (), officially the Republic of Liberia, is a country on the West African coast. It is bordered by Sierra Leone to Liberia–Sierra Leone border, its northwest, Guinea to its north, Ivory Coast to its east, and the Atlantic Ocean ...

. Traditional

Burmese units of measurement The traditional Burmese units of measurement were a system of measurement used in Myanmar (also known as Burma). According to the 2010 CIA Factbook, Myanmar is one of three countries that have not adopted the International System of Units (SI ...

are used in

Burma Myanmar, ; UK pronunciations: US pronunciations incl. . Note: Wikipedia's IPA conventions require indicating /r/ even in British English although only some British English speakers pronounce r at the end of syllables. As John Wells explai ...

. U.S. units are used in limited contexts in Canada due to the large volume of trade; there is also considerable use of imperial weights and measures, despite ''de jure'' Canadian conversion to metric. A number of other jurisdictions have laws mandating or permitting other systems of measurement in some or all contexts, such as the United Kingdom – whose road signage legislation, for instance, only allows distance signs displaying

imperial units 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 thro ...

(miles or yards) – or Hong Kong.HK Weights and Measures Ordinance
/ref> In the United States, metric units are used almost universally in science, widely in the military, and partially in industry, but customary units predominate in household use. At retail stores, the litre (spelled 'liter' in the U.S.) is a commonly used unit for volume, especially on bottles of beverages, and milligrams, rather than grains, are used for medications. Some other non- SI units are still in international use, such as

s and

knots A knot is a fastening in rope or interwoven lines. Knot may also refer to: Places * Knot, Nancowry, a village in India Archaeology * Knot of Isis (tyet), symbol of welfare/life. * Minoan snake goddess figurines#Sacral knot Arts, entertainme ...

in aviation and shipping.

Metric system

Metric system The metric system is a system of measurement that succeeded the Decimal, decimalised system based on the metre that had been introduced in French Revolution, France in the 1790s. The historical development of these systems culminated in the d ...

s of units have evolved since the adoption of the first well-defined system in France in 1795. During this evolution the use of these systems has spread throughout the world, first to non-English-speaking countries, and then to English speaking countries. Multiples and submultiples of metric units are related by powers of ten and their names are formed with

prefixes A prefix is an affix which is placed before the Word stem, stem of a word. Adding it to the beginning of one word changes it into another word. For example, when the prefix ''un-'' is added to the word ''happy'', it creates the word ''unhappy'' ...

. This relationship is compatible with the decimal system of numbers and it contributes greatly to the convenience of metric units. In the early metric system there were two base units, the

for length and the

gram The gram (originally gramme; SI unit symbol g) is a Physical unit, 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 wate ...

for mass. The other units of length and mass, and all units of area, volume, and derived units such as density were derived from these two base units.

Mesures usuelles Mesures usuelles (, ''customary measurements'') were a French system of measurement introduced by Napoleon I in 1812 to act as compromise between the metric system and traditional measurements. The system was restricted to use in the retail indust ...

( French for ''customary measurements'') were a system of measurement introduced as a compromise between the metric system and traditional measurements. It was used in France from 1812 to 1839. A number of variations on the metric system have been in use. These include gravitational systems, the centimetre–gram–second systems (cgs) useful in science, the metre–tonne–second system (mts) once used in the USSR and the metre–kilogram–second system (mks). In some engineering fields, like

computer-aided design Computer-aided design (CAD) is the use of computers (or ) to aid in the creation, modification, analysis, or optimization of a design. This software is used to increase the productivity of the designer, improve the quality of design, improve c ...

, millimetre–gram–second (mmgs) is also used. The current international standard for the metric system is the

( or SI). It is a system in which all units can be expressed in terms of seven units. The units that serves as the

SI base unit The SI base units are the standard units of measurement defined by the International System of Units (SI) for the seven base quantities of what is now known as the International System of Quantities: they are notably a basic set from which all ...

s are the

kilogram 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 ...

second The second (symbol: s) is the unit of time in the International System of Units (SI), historically defined as of a day – this factor derived from the division of the day first into 24 hours, then to 60 minutes and finally to 60 seconds ...

ampere The ampere (, ; symbol: A), often shortened to amp,SI supports only the use of symbols and deprecates the use of abbreviations for units. is the unit of electric current in the International System of Units (SI). One ampere is equal to elect ...

kelvin The kelvin, symbol K, is the primary unit of temperature in the International System of Units (SI), used alongside its prefixed forms and the degree Celsius. It is named after the Belfast-born and University of Glasgow-based engineer and phys ...

mole Mole (or Molé) may refer to: Animals * Mole (animal) or "true mole", mammals in the family Talpidae, found in Eurasia and North America * Golden moles, southern African mammals in the family Chrysochloridae, similar to but unrelated to Talpida ...

, and

candela The candela ( or ; symbol: cd) is the unit of luminous intensity in the International System of Units (SI). It measures luminous power per unit solid angle emitted by a light source in a particular direction. Luminous intensity is analogous to ...

Imperial and US customary units

Both

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 ...

s and

derive from earlier

English unit English units are the units of measurement used in England up to 1826 (when they were replaced by Imperial units), which evolved as a combination of the Anglo-Saxon and Roman systems of units. Various standards have applied to English units at d ...

s. Imperial units were mostly used in the former

British Empire The British Empire was composed of the dominions, colonies, protectorates, mandates, and other territories ruled or administered by the United Kingdom and its predecessor states. It began with the overseas possessions and trading posts esta ...

and the

British Commonwealth The Commonwealth of Nations, simply referred to as the Commonwealth, is a political association of 56 member states, the vast majority of which are former territories of the British Empire. The chief institutions of the organisation are the Co ...

, but in all these countries they have been largely supplanted by the metric system. They are still used for some applications in the United Kingdom but have been mostly replaced by the metric system in

commercial Commercial may refer to: * a dose of advertising conveyed through media (such as - for example - radio or television) ** Radio advertisement ** Television advertisement * (adjective for:) commerce, a system of voluntary exchange of products and s ...

scientific Science is a systematic endeavor that builds and organizes knowledge in the form of testable explanations and predictions about the universe. Science may be as old as the human species, and some of the earliest archeological evidence for ...

, and

industrial Industrial may refer to: Industry * Industrial archaeology, the study of the history of the industry * Industrial engineering, engineering dealing with the optimization of complex industrial processes or systems * Industrial city, a city dominate ...

applications. US customary units, however, are still the main system of measurement in the

. While some steps towards

metrication Metrication or metrification is the act or process of converting to the metric system of measurement. All over the world, countries have transitioned from local and traditional units of measurement to the metric system. This process began in F ...

have been made (mainly in the late 1960s and early 1970s), the customary units have a strong hold due to the vast industrial infrastructure and commercial development. While imperial and US customary systems are closely related, there are a number of differences between them. Units of length and area (the

foot The foot ( : feet) is an anatomical structure found in many vertebrates. It is the terminal portion of a limb which bears weight and allows locomotion. In many animals with feet, the foot is a separate organ at the terminal part of the leg made ...

yard The yard (symbol: yd) is an English unit of length in both the British imperial and US customary systems of measurement equalling 3 feet or 36 inches. Since 1959 it has been by international agreement standardized as exactly ...

, etc.) have been identical since the adoption of the International Yard and Pound Agreement; however, America and, formerly, India retained older definitions for surveying purposes. This gave rise to the US survey foot for instance. The avoirdupois units of mass and weight differ for units larger than a pound (lb). The imperial system uses a stone of 14 lb, a long

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 ...

of 112 lb and a long

ton Ton is the name of any one of several units of measure. It has a long history and has acquired several meanings and uses. Mainly it describes units of weight. Confusion can arise because ''ton'' can mean * the long ton, which is 2,240 pounds ...

of 2240 lb. The stone is not used in the US and the hundredweights and tons are short: 100 lb and 2000 lb respectively. Where these systems most notably differ is in their units of volume. A US

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 St ...

(fl oz), about 29.6

millilitre The litre (international spelling) or liter (American English spelling) (SI symbols L and l, other symbol used: ℓ) is a metric unit of volume. It is equal to 1 cubic decimetre (dm3), 1000 cubic centimetres (cm3) or 0.001 cubic metre (m3) ...

s (ml), is slightly larger than the imperial fluid ounce (about 28.4 ml). However, as there are 16 US fl oz to a US

pint The pint (, ; symbol pt, sometimes abbreviated as ''p'') is a unit of volume or capacity in both the imperial unit, imperial and United States customary units, United States customary measurement systems. In both of those systems it is tradition ...

and 20 imp fl oz per imperial pint, the imperial pint is about 20% larger. The same is true of

quart The quart (symbol: qt) is an English unit of volume equal to a quarter gallon. Three kinds of quarts are currently used: the liquid quart and dry quart of the US customary system and the of the British imperial system. All are roughly equ ...

gallon The gallon is a unit of volume in imperial units and United States customary units. Three different versions are in current use: *the imperial gallon (imp gal), defined as , which is or was used in the United Kingdom, Ireland, Canada, Austr ...

s, etc.; six US gallons are a little less than five imperial gallons. The avoirdupois system served as the general system of mass and weight. In addition to this there are the

troy Troy ( el, Τροία and Latin: Troia, Hittite language, Hittite: 𒋫𒊒𒄿𒊭 ''Truwiša'') or Ilion ( el, Ίλιον and Latin: Ilium, Hittite language, Hittite: 𒃾𒇻𒊭 ''Wiluša'') was an ancient city located at Hisarlik in prese ...

and the

apothecaries' system The apothecaries' system, or apothecaries' weights and measures, is a historical system of mass and volume units that were used by physicians and apothecaries for medical prescriptions and also sometimes by scientists."Medicinal-Gewicht, Apotheke ...

s. Troy weight was customarily used for

precious metal Precious metals are rare, naturally occurring metallic chemical elements of high economic value. Chemically, the precious metals tend to be less reactive than most elements (see noble metal). They are usually ductile and have a high lustre. ...

black powder Gunpowder, also commonly known as black powder to distinguish it from modern smokeless powder, is the earliest known chemical explosive. It consists of a mixture of sulfur, carbon (in the form of charcoal) and potassium nitrate (saltpeter). Th ...

and

gemstone A gemstone (also called a fine gem, jewel, precious stone, or semiprecious stone) is a piece of mineral crystal which, in cut and polished form, is used to make jewelry or other adornments. However, certain rocks (such as lapis lazuli, opal, ...

s. The troy ounce is the only unit of the system in current use; it is used for precious metals. Although the troy ounce is larger than its avoirdupois equivalent, the pound is smaller. The obsolete troy pound was divided into 12 ounces, rather than the 16 ounces per pound of the avoirdupois system. The apothecaries' system was traditionally used in

pharmacology Pharmacology is a branch of medicine, biology and pharmaceutical sciences concerned with drug or medication action, where a drug may be defined as any artificial, natural, or endogenous (from within the body) molecule which exerts a biochemica ...

, but has now been replaced by the metric system; it shared the same pound and ounce as the troy system but with different further subdivisions.

Natural units

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 Coherence (units of measurement), coherent unit of a quantity. For e ...

are

defined in terms of universal

physical constants A physical constant, sometimes fundamental physical constant or universal constant, is a physical quantity that is generally believed to be both universal in nature and have constant value in time. It is contrasted with a mathematical constant, ...

in such a manner that selected physical constants take on the numerical value of one when expressed in terms of those units. Natural units are so named because their definition relies on only properties of

nature Nature, in the broadest sense, is the physics, physical world or universe. "Nature" can refer to the phenomenon, phenomena of the physical world, and also to life in general. The study of nature is a large, if not the only, part of science. ...

and not on any human construct. Varying systems of natural units are possible, depending on the choice of constants used. Some examples are as follows: *

Geometrized unit system A geometrized unit system, geometric unit system or geometrodynamic unit system is a system of natural units in which the base physical units are chosen so that the speed of light in vacuum, ''c'', and the gravitational constant, ''G'', are set eq ...

s are useful in

relativistic physics In physics, relativistic mechanics refers to mechanics compatible with special relativity (SR) and general relativity (GR). It provides a non-quantum mechanics, quantum mechanical description of a system of particles, or of a fluid, in cases where ...

. In these systems,

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 ...

and the

gravitational constant The gravitational constant (also known as the universal gravitational constant, the Newtonian constant of gravitation, or the Cavendish gravitational constant), denoted by the capital letter , is an empirical physical constant involved in ...

are among the constants chosen. * Planck units is system of geometrized units in which the

reduced Planck constant The Planck constant, or Planck's constant, is a fundamental physical constant of foundational importance in quantum mechanics. The constant gives the relationship between the energy of a photon and its frequency, and by the mass-energy equivale ...

is included in the list of defining constants. It is based on only properties of

free space A vacuum is a space devoid of matter. The word is derived from the Latin adjective ''vacuus'' for "vacant" or "void". An approximation to such vacuum is a region with a gaseous pressure much less than atmospheric pressure. Physicists often dis ...

rather than of any object or particle. * Stoney units is a system of geometrized units in which the Coulomb constant and the

elementary charge The elementary charge, usually denoted by is the electric charge carried by a single proton or, equivalently, the magnitude of the negative electric charge carried by a single electron, which has charge −1 . This elementary charge is a fundame ...

are included. *

Hartree atomic units The Hartree atomic units are a system of natural units of measurement which is especially convenient for atomic physics and computational chemistry calculations. They are named after the physicist Douglas Hartree. By definition, the following four ...

are a system of units used in

atomic physics Atomic physics is the field of physics that studies atoms as an isolated system of electrons and an atomic nucleus. Atomic physics typically refers to the study of atomic structure and the interaction between atoms. It is primarily concerned wit ...

, particularly for describing the properties of

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 kn ...

s. The atomic units have been chosen to use several constants relating to the electron: the

electron mass The electron mass (symbol: ''m''e) is the mass of a stationary electron, also known as the invariant mass of the electron. It is one of the fundamental constants of physics. It has a value of about or about , which has an energy-equivalent of ...

, the

, the Coulomb constant and the

. The unit of

energy In physics, energy (from Ancient Greek: ἐνέργεια, ''enérgeia'', “activity”) is the quantitative property that is transferred to a body or to a physical system, recognizable in the performance of work and in the form of heat a ...

in this system is the total energy of the

in the

Bohr atom In atomic physics, the Bohr model or Rutherford–Bohr model, presented by Niels Bohr and Ernest Rutherford in 1913, is a system consisting of a small, dense nucleus surrounded by orbiting electrons—similar to the structure of the Solar Syste ...

and called the

Hartree energy The hartree (symbol: ''E''h or Ha), also known as the Hartree energy, is the unit of energy in the Hartree atomic units system, named after the British physicist Douglas Hartree. Its CODATA recommended value is = The hartree energy is approxima ...

. The unit of length is the

Bohr radius The Bohr radius (''a''0) is a physical constant, approximately equal to the most probable distance between the nucleus and the electron in a hydrogen atom in its ground state. It is named after Niels Bohr, due to its role in the Bohr model of an ...

Non-standard units

Non-standard measurement units also found in books, newspapers etc., include:

Area

* The

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 ...

, which has a playing area long by wide. This is often used by the

American American(s) may refer to: * American, something of, from, or related to the United States of America, commonly known as the "United States" or "America" ** Americans, citizens and nationals of the United States of America ** American ancestry, pe ...

public media for the sizes of large buildings or parks. It is used both as a unit of length (, the length of the playing field excluding goal areas) and as a unit of area (), about . * British media also frequently uses the

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 tu ...

for equivalent purposes, although

soccer Association football, more commonly known as football or soccer, is a team sport played between two teams of 11 players who primarily use their feet to propel the ball around a rectangular field called a pitch. The objective of the game is ...

pitches are not of a fixed size, but instead can vary within defined limits ( long, and wide, giving an area of ). However 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 competit ...

field must be exactly giving an area of or . For example, " HSS vessels are aluminium catamarans about the size of a football pitch." * Larger areas are also expressed as a multiple of the areas of certain American states, or subdivisions of the UK etc.

Energy

* A ton of

TNT equivalent TNT equivalent is a convention for expressing energy, typically used to describe the energy released in an explosion. The is a unit of energy defined by that convention to be , which is the approximate energy released in the detonation of a m ...

, and its multiples the kiloton, the megaton, and the gigaton. Often used in stating the power of very energetic events such as

explosion An explosion is a rapid expansion in volume associated with an extreme outward release of energy, usually with the generation of high temperatures and release of high-pressure gases. Supersonic explosions created by high explosives are known ...

s and

volcanic A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most often found where tectonic plates a ...

events and

earthquakes 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, from ...

and

asteroid An asteroid is a minor planet of the inner Solar System. Sizes and shapes of asteroids vary significantly, ranging from 1-meter rocks to a dwarf planet almost 1000 km in diameter; they are rocky, metallic or icy bodies with no atmosphere. ...

impacts. A

of TNT as a unit of

has been defined as 1000 thermochemical calories (). * The atom bomb dropped on Hiroshima. Its energy yield is often used in the

public media Public broadcasting involves radio, television and other electronic media outlets whose primary mission is public service. Public broadcasters receive funding from diverse sources including license fees, individual contributions, public financing ...

and popular

books A book is a medium for recording information in the form of writing or images, typically composed of many pages (made of papyrus, parchment, vellum, or paper) bound together and protected by a cover. The technical term for this physical ar ...

as a unit of energy. (Its yield was roughly 13 kilotons, or 60 TJ.) * One stick of

dynamite Dynamite is an explosive made of nitroglycerin, sorbents (such as powdered shells or clay), and Stabilizer (chemistry), stabilizers. It was invented by the Swedish people, Swedish chemist and engineer Alfred Nobel in Geesthacht, Northern Germa ...

Units of currency

A unit of measurement that applies to

money Money is any item or verifiable record that is generally accepted as payment for goods and services and repayment of debts, such as taxes, in a particular country or socio-economic context. The primary functions which distinguish money are as ...

is called a

unit of account In economics, unit of account is one of the money functions. A unit of account is a standard numerical monetary unit of measurement of the market value of goods, services, and other transactions. Also known as a "measure" or "standard" of rela ...

in economics and unit of measure in accounting. This is normally a

currency A currency, "in circulation", from la, currens, -entis, literally meaning "running" or "traversing" is a standardization of money in any form, in use or circulation as a medium of exchange, for example banknotes and coins. A more general def ...

issued by a

country A country is a distinct part of the world, such as a state, nation, or other political entity. It may be a sovereign state or make up one part of a larger state. For example, the country of Japan is an independent, sovereign state, while the ...

or a fraction thereof; for instance, the

US dollar The United States dollar (symbol: $; code: USD; also abbreviated US$ or U.S. Dollar, to distinguish it from other dollar-denominated currencies; referred to as the dollar, U.S. dollar, American dollar, or colloquially buck) is the official ...

and US cent ( of a dollar), or the

euro The euro ( symbol: €; code: EUR) is the official currency of 19 out of the member states of the European Union (EU). This group of states is known as the eurozone or, officially, the euro area, and includes about 340 million citizens . ...

and euro cent.

ISO 4217 ISO 4217 is a standard published by the International Organization for Standardization (ISO) that defines alpha codes and numeric codes for the representation of currencies and provides information about the relationships between individual cu ...

is the international standard describing three letter codes (also known as the currency code) to define the names of currencies established by the International Organization for Standardization (ISO).

Historical systems of measurement

Throughout history, many official systems of measurement have been used. While no longer in official use, some of these customary systems are occasionally used in day-to-day life, for instance in

cooking Cooking, cookery, or culinary arts is the art, science and craft of using heat to Outline of food preparation, prepare food for consumption. Cooking techniques and ingredients vary widely, from grilling food over an open fire to using electric ...

Africa

Algerian Algerian may refer to: * Something of, or related to Algeria * Algerian people This article is about the demographic features of the population of Algeria, including population density, ethnicity, education level, health of the populace, econo ...

Egyptian Egyptian describes something of, from, or related to Egypt. Egyptian or Egyptians may refer to: Nations and ethnic groups * Egyptians, a national group in North Africa ** Egyptian culture, a complex and stable culture with thousands of years of ...

Ethiopian Ethiopians are the native inhabitants of Ethiopia, as well as the global diaspora of Ethiopia. Ethiopians constitute several component ethnic groups, many of which are closely related to ethnic groups in neighboring Eritrea and other parts of ...

* Eritrean *

Guinean Guinea ( ),, fuf, 𞤘𞤭𞤲𞤫, italic=no, Gine, wo, Gine, nqo, ߖߌ߬ߣߍ߫, bm, Gine officially the Republic of Guinea (french: République de Guinée), is a coastal country in West Africa. It borders the Atlantic Ocean to the we ...

Libyan Demographics of Libya is the demography of Libya, specifically covering population density, ethnicity, education level, health of the populace, economic status, and religious affiliations, as well as other aspects of the Libyan population. The ...

* Malagasy *

Mauritian Mauritians (singular Mauritian; french: Mauricien; Creole: ''Morisien'') are nationals or natives of the Republic of Mauritius and their descendants. Mauritius is a multi-ethnic society, with notable groups of people of South Asian (notably ...

* Moroccan *

Seychellois This article is about the demographic features of the population of Seychelles, including population density, ethnicity, education level, health of the populace, economic status, religious affiliations and other aspects of the population. About ...

* Somalian * Tunisian * South African *

Tanzanian Tanzania (; ), officially the United Republic of Tanzania ( sw, Jamhuri ya Muungano wa Tanzania), is a country in East Africa within the African Great Lakes region. It borders Uganda to the north; Kenya to the northeast; Comoro Islands and ...

Asia

Arabic Arabic (, ' ; , ' or ) is a Semitic languages, Semitic language spoken primarily across the Arab world.Semitic languages: an international handbook / edited by Stefan Weninger; in collaboration with Geoffrey Khan, Michael P. Streck, Janet C ...

M. Ismail Marcinkowski, ''Measures and Weights in the Islamic World. An English Translation of Professor Walther Hinz's Handbook "Islamische Maße und Gewichte"'', with a foreword by Professor Bosworth, F.B.A. Kuala Lumpur, ISTAC, 2002, . This work is an annotated translation of a work in German by the late German orientalist Walther Hinz, published in the ''Handbuch der Orientalistik'', erste Abteilung, Ergänzungsband I, Heft 1, Leiden, The Netherlands: E. J. Brill, 1970. * Afgan *

Cambodian Cambodian usually refers to: * Something of, from, or related to the country of Cambodia ** Cambodian people (or Khmer people) ** Cambodian language (or Khmer language) ** For citizens and nationals of Cambodia, see Demographics of Cambodia ** Fo ...

Chinese Chinese can refer to: * Something related to China * Chinese people, people of Chinese nationality, citizenship, and/or ethnicity **''Zhonghua minzu'', the supra-ethnic concept of the Chinese nation ** List of ethnic groups in China, people of ...

Hebrew Hebrew (; ; ) is a Northwest Semitic language of the Afroasiatic language family. Historically, it is one of the spoken languages of the Israelites and their longest-surviving descendants, the Jews and Samaritans. It was largely preserved ...

(

Biblical 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 of a ...

and

Talmud The Talmud (; he, , Talmūḏ) is the central text of Rabbinic Judaism and the primary source of Jewish religious law (''halakha'') and Jewish theology. Until the advent of modernity, in nearly all Jewish communities, the Talmud was the cente ...

ic) *

Hindu Hindus (; ) are people who religiously adhere to Hinduism.Jeffery D. Long (2007), A Vision for Hinduism, IB Tauris, , pages 35–37 Historically, the term has also been used as a geographical, cultural, and later religious identifier for ...

Indonesian Indonesian is anything of, from, or related to Indonesia, an archipelagic country in Southeast Asia. It may refer to: * Indonesians, citizens of Indonesia ** Native Indonesians, diverse groups of local inhabitants of the archipelago ** Indonesian ...

Japanese Japanese may refer to: * Something from or related to Japan, an island country in East Asia * Japanese language, spoken mainly in Japan * Japanese people, the ethnic group that identifies with Japan through ancestry or culture ** Japanese diaspor ...

Korean Korean may refer to: People and culture * Koreans, ethnic group originating in the Korean Peninsula * Korean cuisine * Korean culture * Korean language **Korean alphabet, known as Hangul or Chosŏn'gŭl **Korean dialects and the Jeju language ** ...

Omani Oman ( ; ar, عُمَان ' ), officially the Sultanate of Oman ( ar, سلْطنةُ عُمان ), is an Arabian country located in southwestern Asia. It is situated on the southeastern coast of the Arabian Peninsula, and spans the mouth of t ...

* Pakistani *

Philippine The Philippines (; fil, Pilipinas, links=no), officially the Republic of the Philippines ( fil, Republika ng Pilipinas, links=no), * bik, Republika kan Filipinas * ceb, Republika sa Pilipinas * cbk, República de Filipinas * hil, Republ ...

Mesopotamian Mesopotamia ''Mesopotamíā''; ar, بِلَاد ٱلرَّافِدَيْن or ; syc, ܐܪܡ ܢܗܪ̈ܝܢ, or , ) is a historical region of Western Asia situated within the Tigris–Euphrates river system, in the northern part of the F ...

Persian Persian may refer to: * People and things from Iran, historically called ''Persia'' in the English language ** Persians, the majority ethnic group in Iran, not to be conflated with the Iranic peoples ** Persian language, an Iranian language of the ...

Singaporean Singaporeans, or the Singaporean people, refers to citizens or people who identify with the sovereign island city-state of Singapore. Singapore is a multi-ethnic, multi-cultural and multi-lingual country. Singaporeans of Chinese, Malay, India ...

* Sri Lankan *

Syrian Syrians ( ar, سُورِيُّون, ''Sūriyyīn'') are an Eastern Mediterranean ethnic group indigenous to the Levant. They share common Levantine Semitic roots. The cultural and linguistic heritage of the Syrian people is a blend of both indi ...

Taiwanese Taiwanese may refer to: * Taiwanese language, another name for Taiwanese Hokkien * Something from or related to Taiwan ( Formosa) * Taiwanese aborigines, the indigenous people of Taiwan * Han Taiwanese, the Han people of Taiwan * Taiwanese people, ...

Tamil Tamil may refer to: * Tamils, an ethnic group native to India and some other parts of Asia **Sri Lankan Tamils, Tamil people native to Sri Lanka also called ilankai tamils **Tamil Malaysians, Tamil people native to Malaysia * Tamil language, nativ ...

Thai Thai or THAI may refer to: * Of or from Thailand, a country in Southeast Asia ** Thai people, the dominant ethnic group of Thailand ** Thai language, a Tai-Kadai language spoken mainly in and around Thailand *** Thai script *** Thai (Unicode block ...

Vietnamese Vietnamese may refer to: * Something of, from, or related to Vietnam, a country in Southeast Asia ** A citizen of Vietnam. See Demographics of Vietnam. * Vietnamese people, or Kinh people, a Southeast Asian ethnic group native to Vietnam ** Overse ...

* Nepalese Still in use: *

Myanmar Myanmar, ; UK pronunciations: US pronunciations incl. . Note: Wikipedia's IPA conventions require indicating /r/ even in British English although only some British English speakers pronounce r at the end of syllables. As John C. Wells, Joh ...

Europe

Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic peri ...

Belgian Belgian may refer to: * Something of, or related to, Belgium * Belgians, people from Belgium or of Belgian descent * Languages of Belgium, languages spoken in Belgium, such as Dutch, French, and German *Ancient Belgian language, an extinct languag ...

Byzantine The Byzantine Empire, also referred to as the Eastern Roman Empire or Byzantium, was the continuation of the Roman Empire primarily in its eastern provinces during Late Antiquity and the Middle Ages, when its capital city was Constantinopl ...

Czech Czech may refer to: * Anything from or related to the Czech Republic, a country in Europe ** Czech language ** Czechs, the people of the area ** Czech culture ** Czech cuisine * One of three mythical brothers, Lech, Czech, and Rus' Places * Czech, ...

Cypriot Cypriot (in older sources often "Cypriote") refers to someone or something of, from, or related to the country of Cyprus. * Cypriot people, or of Cypriot descent; this includes: **Armenian Cypriots **Greek Cypriots **Maronite Cypriots **Turkish C ...

Danish Danish may refer to: * Something of, from, or related to the country of Denmark People * A national or citizen of Denmark, also called a "Dane," see Demographics of Denmark * Culture of Denmark * Danish people or Danes, people with a Danish a ...

Dutch Dutch commonly refers to: * Something of, from, or related to the Netherlands * Dutch people () * Dutch language () Dutch may also refer to: Places * Dutch, West Virginia, a community in the United States * Pennsylvania Dutch Country People E ...

English English usually refers to: * English language * English people English may also refer to: Peoples, culture, and language * ''English'', an adjective for something of, from, or related to England ** English national ide ...

* Estonian *

Finnish Finnish may refer to: * Something or someone from, or related to Finland * Culture of Finland * Finnish people or Finns, the primary ethnic group in Finland * Finnish language, the national language of the Finnish people * Finnish cuisine See also ...

* French (now) * French (to 1795) *

German German(s) may refer to: * Germany (of or related to) ** Germania (historical use) * Germans, citizens of Germany, people of German ancestry, or native speakers of the German language ** For citizens of Germany, see also German nationality law **Ge ...

Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...

Hungary Hungary ( hu, Magyarország ) is a landlocked country in Central Europe. Spanning of the Carpathian Basin, it is bordered by Slovakia to the north, Ukraine to the northeast, Romania to the east and southeast, Serbia to the south, Croatia a ...

* Icelandic *

Irish Irish may refer to: Common meanings * Someone or something of, from, or related to: ** Ireland, an island situated off the north-western coast of continental Europe ***Éire, Irish language name for the isle ** Northern Ireland, a constituent unit ...

Italian Italian(s) may refer to: * Anything of, from, or related to the people of Italy over the centuries ** Italians, an ethnic group or simply a citizen of the Italian Republic or Italian Kingdom ** Italian language, a Romance language *** Regional Ita ...

* Latvian *

Luxembourgian Luxembourgish ( ; also ''Luxemburgish'', ''Luxembourgian'', ''Letzebu(e)rgesch''; Luxembourgish: ) is a West Germanic language that is spoken mainly in Luxembourg. About 400,000 people speak Luxembourgish worldwide. As a standard form of th ...

* Maltese *

Norwegian Norwegian, Norwayan, or Norsk may refer to: *Something of, from, or related to Norway, a country in northwestern Europe * Norwegians, both a nation and an ethnic group native to Norway * Demographics of Norway *The Norwegian language, including ...

Polish Polish may refer to: * Anything from or related to Poland, a country in Europe * Polish language * Poles Poles,, ; singular masculine: ''Polak'', singular feminine: ''Polka'' or Polish people, are a West Slavic nation and ethnic group, w ...

Portuguese Portuguese may refer to: * anything of, from, or related to the country and nation of Portugal ** Portuguese cuisine, traditional foods ** Portuguese language, a Romance language *** Portuguese dialects, variants of the Portuguese language ** Portu ...

Roman Roman or Romans most often refers to: *Rome, the capital city of Italy *Ancient Rome, Roman civilization from 8th century BC to 5th century AD *Roman people, the people of ancient Rome *''Epistle to the Romans'', shortened to ''Romans'', a letter ...

Romanian Romanian may refer to: *anything of, from, or related to the country and nation of Romania **Romanians, an ethnic group **Romanian language, a Romance language *** Romanian dialects, variants of the Romanian language ** Romanian cuisine, tradition ...

Russian Russian(s) refers to anything related to Russia, including: *Russians (, ''russkiye''), an ethnic group of the East Slavic peoples, primarily living in Russia and neighboring countries *Rossiyane (), Russian language term for all citizens and peo ...

* Scottish * Serbian * Slovak *

Spanish Spanish might refer to: * Items from or related to Spain: **Spaniards are a nation and ethnic group indigenous to Spain **Spanish language, spoken in Spain and many Latin American countries **Spanish cuisine Other places * Spanish, Ontario, Can ...

Swedish Swedish or ' may refer to: Anything from or related to Sweden, a country in Northern Europe. Or, specifically: * Swedish language, a North Germanic language spoken primarily in Sweden and Finland ** Swedish alphabet, the official alphabet used by ...

Switzerland ). Swiss law does not designate a ''capital'' as such, but the federal parliament and government are installed in Bern, while other federal institutions, such as the federal courts, are in other cities (Bellinzona, Lausanne, Luzern, Neuchâtel ...

* Turkish *

Tatar The Tatars ()Tatar
in the Collins English Dictionary is an umbrella term for different

Welsh Welsh may refer to: Related to Wales * Welsh, referring or related to Wales * Welsh language, a Brittonic Celtic language spoken in Wales * Welsh people People * Welsh (surname) * Sometimes used as a synonym for the ancient Britons (Celtic peop ...

North America

Costa Rican Costa Rica (, ; ; literally "Rich Coast"), officially the Republic of Costa Rica ( es, República de Costa Rica), is a country in the Central American region of North America, bordered by Nicaragua to the north, the Caribbean Sea to the no ...

Cuban Cuban may refer to: * Something of, from, or related to Cuba, a country in the Caribbean * Cubans, people from Cuba, or of Cuban descent ** Cuban exile, a person who left Cuba for political reasons, or a descendant thereof * Cuban citizen, a perso ...

* Haitian * Honduran *

Mexico Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...

Nicaraguan Nicaragua (; ), officially the Republic of Nicaragua (), is the largest country in Central America, bordered by Honduras to the north, the Caribbean to the east, Costa Rica to the south, and the Pacific Ocean to the west. Managua is the countr ...

* Puerto Rican

South America

Argentine Argentines (mistakenly translated Argentineans in the past; in Spanish (masculine) or (feminine)) are people identified with the country of Argentina. This connection may be residential, legal, historical or cultural. For most Argentines, s ...

Bolivian Bolivian may refer to: * Something of, or related to Bolivia ** Bolivian people ** Demographics of Bolivia ** Culture of Bolivia * SS ''Bolivian'', a British-built standard cargo ship A cargo ship or freighter is a merchant ship that carries ...

* Brazilian * Chilean * Colombian *

Paraguayan Paraguay (; ), officially the Republic of Paraguay ( es, República del Paraguay, links=no; gn, Tavakuairetã Paraguái, links=si), is a landlocked country in South America. It is bordered by Argentina to the south and southwest, Brazil to th ...

Peruvian Peruvians ( es, peruanos) are the citizens of Peru. There were Andean and coastal ancient civilizations like Caral, which inhabited what is now Peruvian territory for several millennia before the Spanish conquest in the 16th century; Peruvian p ...

Uruguayan 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 ...

Venezuelan Venezuela (; ), officially the Bolivarian Republic of Venezuela ( es, link=no, República Bolivariana de Venezuela), is a country on the northern coast of South America, consisting of a continental landmass and many islands and islets in th ...

Ancient

* Biblical and Talmudic *

Indian Indian or Indians may refer to: Peoples South Asia * Indian people, people of Indian nationality, or people who have an Indian ancestor ** Non-resident Indian, a citizen of India who has temporarily emigrated to another country * South Asia ...

Notes and references

Bibliography

* Tavernor, Robert (2007), ''Smoot's Ear: The Measure of Humanity'',

External links

CLDR - Unicode localization of currency, date, time, numbersA Dictionary of Units of Measurement
*Reasonover's Land Measure

* ttps://web.archive.org/web/20060226162744/http://aurora.regenstrief.org/~schadow/units/UCUM/ucum.html The Unified Code for Units of Measure {{SI units * Measurement Conceptual systems