Measuring tape with inches
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The inch (symbol: in or
″) is a
unit
Unit may refer to:
Arts and entertainment
* UNIT, a fictional military organization in the science fiction television series ''Doctor Who''
* Unit of action, a discrete piece of action (or beat) in a theatrical presentation
Music
* ''Unit'' (alb ...
of
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 ...
in the
British imperial
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
United States customary systems 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 ...
. It is equal to
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 0.914 ...
or of a
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 ...
. Derived from the
Roman uncia ("twelfth"), the word ''inch'' is also sometimes used to translate similar units in other measurement systems,
usually understood as deriving from the width of the human thumb.
Standards for the exact length of an inch have varied in the past, but since the adoption of the
international yard
The international yard and pound are two units of measurement that were the subject of an agreement among representatives of six nations signed on 1 July 1959: the United States, United Kingdom, Canada, Australia, New Zealand, and South Africa. T ...
during the 1950s and 1960s the inch has been based on 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 ...
and defined as exactly 25.4
mm.
Name
The English word "inch" ( ang, ynce) was an early borrowing from
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 ...
' ("one-twelfth;
Roman inch
The (plural: ) was a Roman unit of length, weight, and volume. It survived as the Byzantine liquid ounce ( grc-gre, οὐγγία, ''oungía'') and the origin of the English inch, ounce, and fluid ounce.
The Roman inch was equal to of a Rom ...
;
Roman ounce
The (plural: ) was a Roman unit of length, weight, and volume. It survived as the Byzantine liquid ounce ( grc-gre, οὐγγία, ''oungía'') and the origin of the English inch, ounce, and fluid ounce.
The Roman inch was equal to of a Ro ...
"). The vowel change from Latin to Old English (which became Modern English ) is known as
umlaut. The consonant change from the Latin (spelled ''c'') to English is
palatalisation. Both were features of
Old English phonology
Old English phonology is necessarily somewhat speculative since Old English is preserved only as a written language. Nevertheless, there is a very large corpus of the language, and the orthography apparently indicates phonological alternation ...
; see and for more information.
"Inch" is cognate with "
ounce
The ounce () is any of several different units of mass, weight or volume and is derived almost unchanged from the , an Ancient Roman units of measurement, Ancient Roman unit of measurement.
The #International avoirdupois ounce, avoirdupois ounce ...
" ( ang, ynse), whose separate pronunciation and spelling reflect its reborrowing in
Middle English
Middle English (abbreviated to ME) is a form of the English language that was spoken after the Norman conquest of 1066, until the late 15th century. The English language underwent distinct variations and developments following the Old English p ...
from
Anglo-Norman Anglo-Norman may refer to:
*Anglo-Normans, the medieval ruling class in England following the Norman conquest of 1066
* Anglo-Norman language
**Anglo-Norman literature
* Anglo-Norman England, or Norman England, the period in English history from 10 ...
''unce'' and ''ounce''.
In many other European languages, the word for "inch" is the same as or derived from the word for "thumb", as a man's thumb is about an inch wide (and this was even sometimes used to define the inch). In the
Dutch language
Dutch ( ) is a West Germanic language spoken by about 25 million people as a first language and 5 million as a second language. It is the third most widely spoken Germanic language
The Germanic languages are a branch of the Indo-Europea ...
a term for inch is ''engelse duim'' (english thumb). Examples include ca, polzada ("inch") and ' ("thumb"); cs, palec ("thumb"); Danish and no, tomme ("inch") ' ("thumb"); nl, duim (whence af, duim and russian: дюйм); french: pouce; hu, hüvelyk; it, pollice; pt, polegada ("inch") and ' ("thumb"); ("duim"); sk, palec ("thumb"); es, pulgada ("inch") and ' ("thumb"); and sv, tum ("inch") and ''tumme'' ("thumb").
Usage
The inch is a commonly used customary unit of length in the United States, Canada, and the United Kingdom.
[ It is also used in Japan for electronic parts, especially display screens. In most of continental Europe, the inch is also used informally as a measure for display screens. For the United Kingdom, guidance on public sector use states that, since 1 October 1995, without time limit, the inch (along with the foot) is to be used as a primary unit for road signs and related measurements of distance (with the possible exception of clearance heights and widths) and may continue to be used as a secondary or supplementary indication following a metric measurement for other purposes.]
Inches are commonly used to specify the diameter of vehicle wheel rims, and the corresponding inner diameter of tyres in tyre code
Automotive tires are described by an alphanumeric tire code (in North American English) or tyre code (in Commonwealth English), which is generally molded into the sidewall of the tire. This code specifies the dimensions of the tire, and some o ...
s.
The international standard symbol for inch is in (see ISO 31-1
ISO 31-1 is the part of international standard ISO 31 that defines names and symbols for quantities and units related to ''space and time''. It was superseded in 2006 by ISO 80000-3.
Definitions
Its definitions include:
Annex A
Annex ...
, Annex A) but traditionally the inch is denoted by a double prime
The prime symbol , double prime symbol , triple prime symbol , and quadruple prime symbol are used to designate units and for other purposes in mathematics, science, linguistics and music.
Although the characters differ little in appearance fr ...
, which is often approximated by a double quote symbol, and 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 ...
by a prime
A prime number (or a prime) is a natural number greater than 1 that is not a product of two smaller natural numbers. A natural number greater than 1 that is not prime is called a composite number. For example, 5 is prime because the only ways ...
, which is often approximated by an apostrophe
The apostrophe ( or ) is a punctuation mark, and sometimes a diacritical mark, in languages that use the Latin alphabet and some other alphabets. In English, the apostrophe is used for two basic purposes:
* The marking of the omission of one o ...
. For example; ' can be written as 3′ 2″. (This is akin to how the first
First or 1st is the ordinal form of the number one (#1).
First or 1st may also refer to:
*World record, specifically the first instance of a particular achievement
Arts and media Music
* 1$T, American rapper, singer-songwriter, DJ, and rec ...
and second
The second (symbol: s) is the unit of time in the International System of Units (SI), historically defined as of a day – this factor derived from the division of the day first into 24 hours, then to 60 minutes and finally to 60 seconds ...
"cuts" of the hour
An hour (symbol: h; also abbreviated hr) is a unit of time conventionally reckoned as of a day and scientifically reckoned between 3,599 and 3,601 seconds, depending on the speed of Earth's rotation. There are 60 minutes in an hour, and 24 ho ...
are likewise indicated by prime and double prime symbols, and also the first
First or 1st is the ordinal form of the number one (#1).
First or 1st may also refer to:
*World record, specifically the first instance of a particular achievement
Arts and media Music
* 1$T, American rapper, singer-songwriter, DJ, and rec ...
and 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 ...
cuts of the degree
Degree may refer to:
As a unit of measurement
* Degree (angle), a unit of angle measurement
** Degree of geographical latitude
** Degree of geographical longitude
* Degree symbol (°), a notation used in science, engineering, and mathematics
...
.)
Subdivisions of an inch are typically written using dyadic fractions with odd number numerators; for example, ' would be written as ″ and not as 2.375″ nor as ″. However, for engineering purposes fractions are commonly given to three or four places of decimals and have been for many years.
Equivalents
1 international inch is equal to:
* 10,000 ' tenths'
* 1,000 thou
The word ''thou'' is a second-person singular pronoun in English. It is now largely archaic, having been replaced in most contexts by the word ''you'', although it remains in use in parts of Northern England and in Scots (). ''Thou'' is the ...
or mil
* 100 points or gries
* 72 PostScript points
* 10,[ 12, or 40 ]lines
Line most often refers to:
* Line (geometry), object with zero thickness and curvature that stretches to infinity
* Telephone line, a single-user circuit on a telephone communication system
Line, lines, The Line, or LINE may also refer to:
Arts ...
* 6 computer picas
* 3 barleycorns
* 25.4 millimetre
330px, Different lengths as in respect to the electromagnetic spectrum, measured by the metre and its derived scales. The microwave is between 1 meter to 1 millimeter.
The millimetre (American and British English spelling differences#-re, -er, ...
s exactly (1 millimetre ≈ 0.03937008 inches)
* 0.999998 US Survey inches
* or 0.33 palms
* or 0.25 hands
A hand is a prehensile, multi-fingered appendage located at the end of the forearm or forelimb of primates such as humans, chimpanzees, monkeys, and lemurs. A few other vertebrates such as the koala (which has two opposable thumbs on each " ...
* or 0.0833 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 ...
* or 0.0277 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 0.914 ...
s
History
The earliest known reference to the inch in England is from the '' Laws of Æthelberht'' dating to the early 7th century, surviving in a single manuscript, the ''Textus Roffensis
__NOTOC__
The ''Textus Roffensis'' (Latin for "The Tome of Rochester"), fully titled the ''Textus de Ecclesia Roffensi per Ernulphum episcopum'' ("The Tome of the Church of Rochester up to Bishop Ernulf") and sometimes also known as the Anna ...
'' from 1120. Paragraph LXVII sets out the fine for wounds of various depths: one inch, one shilling; two inches, two shillings, etc. Translation (taken from ): If a thigh is pierced right through, 6 shillings compensation shall be paid for each stab. For a stab over an inch eep 1 shilling; for a stab between 2 and 3 inches, 2 shillings; for a stab over 3 inches 3 shillings.
An Anglo-Saxon unit of length was the barleycorn. After 1066, 1 inch was equal to 3 barleycorns, which continued to be its legal definition for several centuries, with the barleycorn being the base unit. One of the earliest such definitions is that of 1324, where the legal definition of the inch was set out in a statute of Edward II of England
Edward II (25 April 1284 – 21 September 1327), also called Edward of Caernarfon, was King of England and Lord of Ireland from 1307 until he was deposed in January 1327. The fourth son of Edward I, Edward became the heir apparent to ...
, defining it as "three grains of barley
Barley (''Hordeum vulgare''), a member of the grass family, is a major cereal grain grown in temperate climates globally. It was one of the first cultivated grains, particularly in Eurasia as early as 10,000 years ago. Globally 70% of barley pr ...
, dry and round, placed end to end, lengthwise".
Similar definitions are recorded in both English and Welsh medieval law tracts. One, dating from the first half of the 10th century, is contained in the Laws of Hywel Dda
Hywel Dda, sometimes anglicised as Howel the Good, or Hywel ap Cadell (died 949/950) was a king of Deheubarth who eventually came to rule most of Wales. He became the sole king of Seisyllwg in 920 and shortly thereafter established Deheubarth ...
which superseded those of Dyfnwal, an even earlier definition of the inch in Wales. Both definitions, as recorded in ''Ancient Laws and Institutes of Wales'' (vol i., pp. 184, 187, 189), are that "three lengths of a barleycorn is the inch".
King David I of Scotland in his Assize of Weights and Measures (c. 1150) is said to have defined the Scottish inch as the width of an average man's thumb at the base of the nail, even including the requirement to calculate the average of a small, a medium, and a large man's measures. However, the oldest surviving manuscripts date from the early 14th century and appear to have been altered with the inclusion of newer material.
In 1814, Charles Butler, a mathematics teacher at Cheam School, recorded the old legal definition of the inch to be "three grains of sound ripe barley being taken out the middle of the ear, well dried, and laid end to end in a row", and placed the barleycorn, not the inch, as the base unit of the English Long Measure system, from which all other units were derived. John Bouvier
John Bouvier (1787 – November 18, 1851), was a French-American jurist and legal lexicographer, is known for his legal writings, particularly his ''Law Dictionary Adapted to the Constitution and Laws of the United States of America and of the S ...
similarly recorded in his 1843 law dictionary that the barleycorn was the fundamental measure. Butler observed, however, that " the length of the barley-corn cannot be fixed, so the inch according to this method will be uncertain", noting that a standard inch measure was now .e. by 1843kept in the Exchequer chamber, Guildhall
A guildhall, also known as a "guild hall" or "guild house", is a historical building originally used for tax collecting by municipalities or merchants in Great Britain and the Low Countries. These buildings commonly become town halls and in som ...
, and ''that'' was the legal definition of the inch.
This was a point also made by George Long in his 1842 '' Penny Cyclopædia'', observing that standard measures had since surpassed the barleycorn definition of the inch, and that to recover the inch measure from its original definition, in case the standard measure were destroyed, would involve the measurement of large numbers of barleycorns and taking their average lengths. He noted that this process would not perfectly recover the standard, since it might introduce errors of anywhere between one hundredth and one tenth of an inch in the definition of a yard.
Before the adoption of the international yard and pound
The international yard and pound are two units of measurement that were the subject of an agreement among representatives of six nations signed on 1 July 1959: the United States, United Kingdom, Canada, Australia, New Zealand, and South Africa. T ...
, various definitions were in use. In the United Kingdom and most countries of 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 ...
, the inch was defined in terms of the Imperial Standard Yard. The United States adopted the conversion factor 1 metre = 39.37 inches by an act in 1866. In 1893, Mendenhall ordered the physical realization of the inch to be based on the international prototype metres numbers 21 and 27, which had been received from the CGPM, together with the previously adopted conversion factor.
As a result of the definitions above, the U.S. inch was effectively defined as 25.4000508 mm (with a reference temperature of 68 degrees Fahrenheit) and the UK inch at 25.399977 mm (with a reference temperature of 62 degrees Fahrenheit). When Carl Edvard Johansson
Carl Edvard Johansson (1864–1943) was a Swedish inventor and scientist.
Johansson invented the gauge block set, also known as "Jo Blocks" ("Johansson gauge blocks"). He was granted his first Swedish patent on 2 May 1901, Swedish patent No. 170 ...
started manufacturing gauge blocks
Gauge blocks (also known as gage blocks, Johansson gauges, slip gauges, or Jo blocks) are a system for producing precision lengths. The individual gauge block is a metal or ceramic block that has been precision ground and lapped to a specific ...
in inch sizes in 1912, Johansson's compromise was to manufacture gauge blocks with a nominal size of 25.4mm, with a reference temperature of 20 degrees Celsius, accurate to within a few parts per million of both official definitions. Because Johansson's blocks were so popular, his blocks became the ''de facto'' standard for manufacturers internationally, with other manufacturers of gauge blocks following Johansson's definition by producing blocks designed to be equivalent to his.
In 1930, the British Standards Institution
The British Standards Institution (BSI) is the national standards body of the United Kingdom. BSI produces technical standards on a wide range of products and services and also supplies certification and standards-related services to busines ...
adopted an inch of exactly 25.4 mm. The American Standards Association
The American National Standards Institute (ANSI ) is a private non-profit organization that oversees the development of voluntary consensus standards
Standardization or standardisation is the process of implementing and developing techn ...
followed suit in 1933. By 1935, industry in 16 countries had adopted the "industrial inch" as it came to be known, effectively endorsing Johansson's pragmatic choice of conversion ratio.
In 1946, the Commonwealth Science Congress recommended a yard of exactly 0.9144 metres for adoption throughout the British Commonwealth. This was adopted by Canada in 1951; the United States on 1 July 1959; Australia in 1961, effective 1 January 1964; and the United Kingdom in 1963, effective on 1 January 1964. The new standards gave an inch of exactly 25.4 mm, 1.7 millionths of an inch longer than the old imperial inch and 2 millionths of an inch shorter than the old US inch.[
]
Related units
US survey inches
The United States retains the -metre definition for surveying, producing a 2 millionth part difference between standard and US survey inches.[A. V. Astin & H. Arnold Karo, (1959)]
''Refinement of values for the yard and the pound''
Washington DC: National Bureau of Standards, republished on National Geodetic Survey web site and the Federal Register (Doc. 59-5442, Filed, 30 June 1959, 8:45 am) This is approximately inch per mile; 12.7 kilometres is exactly standard inches and exactly survey inches. This difference is substantial when doing calculations in State Plane Coordinate Systems with coordinate values in the hundreds of thousands or millions of feet.
In 2020, the U.S. NIST announced that the U.S. survey foot would "be phased out" on 1 January 2023 and be superseded by the International foot (also known as the foot) equal to 0.3048 metres exactly, for all further applications. and by implication, the survey inch with it.
Continental inches
Before the adoption of the metric system, several European countries had customary units whose name translates into "inch". The French '' pouce'' measured roughly 27.0 mm, at least when applied to describe the calibre of artillery pieces. The Amsterdam foot (''voet'') consisted of 11 Amsterdam inches (''duim''). The Amsterdam foot is about 8% shorter than an English foot.
Scottish inch
The now obsolete Scottish inch ( gd, òirleach), of a Scottish foot, was about 1.0016 imperial inches (about ).
See also
* English units
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 ...
* Square inch
A square inch (plural: square inches) is a unit of area, equal to the area of a square with sides of one inch. The following symbols are used to denote square inches:
*square in
*sq inches, sq inch, sq in
*inches/-2, inch/-2, in/-2
*inches^2, inc ...
, Cubic inch
The cubic inch (symbol in3) is a unit of volume in the Imperial units and United States customary units systems. It is the volume of a cube with each of its three dimensions (length, width, and height) being one inch long which is equivalent ...
, and Metric inch
Metric units are units based on the metre, gram or second and decimal (power of ten) multiples or sub-multiples of these. The most widely used examples are the units of the International System of Units (SI). By extension they include units of e ...
* International yard and pound
The international yard and pound are two units of measurement that were the subject of an agreement among representatives of six nations signed on 1 July 1959: the United States, United Kingdom, Canada, Australia, New Zealand, and South Africa. T ...
* Anthropic units
The term anthropic unit (from Greek '' άνθρωπος'' meaning human) is used with different meanings in archaeology, in measurement and in social studies.
In archaeology
In archaeology, ''anthropic units'' are strata, or deposits of mater ...
* Pyramid inch
The pyramid inch is a unit of measure claimed by pyramidologists to have been used in ancient times.
History
The first suggestion that the builders of the Great Pyramid of Giza used units of measure related to modern measures is attributed to O ...
* Digit and Line
Notes
References
Citations
Bibliography
*
{{Authority control
Customary units of measurement in the United States
Imperial units
Units of length
Obsolete Scottish units of measurement
fy:Tomme (lingtemaat)