Inch

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"Inches" redirects here. For other uses, see Inch (disambiguation).

Inch
double prime)[1]
Conversions
1 in in ...... is equal to ...
   Imperial/US units   ⁠1/36⁠ 
SI) units
   25.4 mm
A fire hydrant marked as 3-inch

The inch (symbol: in or

systems of measurement. It is equal to ⁠1/36⁠ yard or ⁠1/12⁠ of a foot. 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 during the 1950s and 1960s the inch has been based on the metric system and defined as exactly 25.4 mm
.

Name

The English word "inch" (

Roman ounce").[2] The vowel change from Latin /u/ to Old English /y/ (which became Modern English /ɪ/) is known as umlaut.[citation needed] The consonant change from the Latin /k/ (spelled c) to English /tʃ/ is palatalisation. Both were features of Old English phonology; see Phonological history of Old English § Palatalization and Germanic umlaut § I-mutation in Old English
for more information.

"Inch" is cognate with "

Old English: ynse), whose separate pronunciation and spelling reflect its reborrowing in Middle English from Anglo-Norman unce and ounce.[3]

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

Afrikaans: duim and Russian: дюйм); French: pouce; Georgian: დუიმი, Hungarian: hüvelyk; Italian: pollice; Portuguese: polegada ("inch") and polegar ("thumb"); ("duim"); Slovak: palec ("thumb"); Spanish: pulgada ("inch") and pulgar ("thumb"); and Swedish
: tum ("inch") and tumme ("thumb").

Usage

Imperial or hybrid countries

The inch is a commonly used customary unit of length in the United States,[7] Canada,[8][9] and the United Kingdom.[10] 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)[11] and may continue to be used as a secondary or supplementary indication following a metric measurement for other purposes.[10]

Worldwide

Inches are used for display screens (e.g. televisions and computer monitors) worldwide. It is the official Japanese standard for electronic parts, especially display screens, and is the industry standard throughout continental Europe for display screens (Germany being one of few countries to supplement it with centimetres in most stores[12]).

Inches are commonly used to specify the diameter of vehicle wheel rims, and the corresponding inner diameter of tyres in

tyre codes.[citation needed
]

Technical details

The international standard symbol for inch is in (see

second cuts of the degree
.)

Subdivisions of an inch are typically written using dyadic fractions with odd number numerators; for example, two and three-eighths of an inch would be written as ⁠2+3/8⁠″ and not as 2.375″ nor as ⁠2+6/16⁠″. However, for engineering purposes fractions are commonly given to three or four places of decimals and have been for many years.[13][14]

Equivalents

1 international inch is equal to:

History

Mid-19th-century tool for converting between different standards of the inch

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 from 1120.[17] Paragraph LXVII sets out the fine for wounds of various depths: one inch, one shilling; two inches, two shillings, etc.[m]

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.[20] 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, defining it as "three grains of barley, dry and round, placed end to end, lengthwise".[20]

Similar definitions are recorded in both English and Welsh medieval law tracts.[21] One, dating from the first half of the 10th century, is contained in the Laws of Hywel Dda 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".[22]

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.[23] However, the oldest surviving manuscripts date from the early 14th century and appear to have been altered with the inclusion of newer material.[24]

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.[25] John Bouvier similarly recorded in his 1843 law dictionary that the barleycorn was the fundamental measure.[26] Butler observed, however, that "[a]s 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 [i.e. by 1843] kept in the Exchequer chamber, Guildhall, and that was the legal definition of the inch.[25]

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.[27]

Before the adoption of the

CGPM, together with the previously adopted conversion factor.[29]

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

gauge blocks 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,[30][31] with other manufacturers of gauge blocks following Johansson's definition by producing blocks designed to be equivalent to his.[32]

In 1930, the British Standards Institution adopted an inch of exactly 25.4 mm. The American Standards Association followed suit in 1933. By 1935, industry in 16 countries had adopted the "industrial inch" as it came to be known,[33][34] effectively endorsing Johansson's pragmatic choice of conversion ratio.[30]

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;[35][36] the United States on 1 July 1959;[37][38][39] Australia in 1961,[40] effective 1 January 1964;[41] and the United Kingdom in 1963,[42] effective on 1 January 1964.[43] 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.[44][45]

US survey inches

The United States retained the ⁠1/39.37⁠-metre definition for surveying, producing a 2 millionth part difference between standard and US survey inches.[45] This is approximately ⁠1/8⁠ inch per mile; 12.7 kilometres is exactly 500,000 standard inches and exactly 499,999 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 National Institute of Standards and Technology 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.[46] This implies that the survey inch was replaced by the international inch.

Continental inches

Main articles:
French inch

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.[47]

Scottish inch

The now obsolete

Scottish Gaelic: òirleach), ⁠1/12⁠ of a Scottish foot, was about 1.0016 imperial inches (about 25.44 mm).[48]

See also

Notes

  1. ^ A tenth of a thou, used in machining.
  2. ^ Used in machining and papermaking.
  3. ^ Formerly used in American English but now often avoided to prevent confusion with millimetres.
  4. ^ Used by the Australian Bureau of Meteorology for measuring rainfall until 1973[15]
  5. ^ a b Part of John Locke's proposal for decimalization of English measures[16]
  6. ^ The typographic point was originally ⁠1/9⁠ of the height of a (capital) letter (cap height) but later acquired a number of different absolute definitions; see Point (typography) § History for details.
  7. gunmaking
    .
  8. ^ Used in botany.
  9. button
    manufacturing.
  10. ^ Used in typography.
  11. ^ Used in American and British shoe sizes.
  12. ^ Used in measuring the height of horses.
  13. Old English: Gif man þeoh þurhstingð, stice ghwilve vi scillingas. Gife ofer ynce, scilling. æt twam yncum, twegen. ofer þry, iii scill. Translation (taken from Attenborough 1922, p. 13): If a thigh is pierced right through, 6 shillings compensation shall be paid for each stab. For a stab over an inch [deep], 1 shilling; for a stab between 2 and 3 inches, 2 shillings; for a stab over 3 inches 3 shillings.[18][19]

References

Citations

  1. ^ Unicode Consortium (2019). "The Unicode Standard 12.1 — General Punctuation ❰ Range: 2000—206F ❱" (PDF). Unicode.org.
  2. ^ "inch, n.1", Oxford English Dictionary, Oxford: Oxford University Press.
  3. ^ "ounce, n.1", Oxford English Dictionary, Oxford: Oxford University Press.
  4. ^ "Inch | unit of measurement". Encyclopedia Britannica. Retrieved 28 March 2019.
  5. ^ "duim - lengtemaat". Genootschap Onze Taal. Retrieved 22 October 2022.
  6. ^ "duim". 24 May 2020. Retrieved 22 October 2022.
  7. ^ "Corpus of Contemporary American English". Brigham Young University. US. Retrieved 5 December 2011. lists 24,302 instances of inch(es) compared to 1548 instances of centimeter(s) and 1343 instances of millimeter(s).
  8. ^ "Weights and Measures Act" (PDF). Canada. 1985. p. 37. Retrieved 11 January 2018 – via Justice Laws Website.
  9. ^ "Weights and Measures Act". Canada. 1 August 2014. p. 2. Retrieved 18 December 2014 – via Justice Laws Website. Canadian units (5) The Canadian units of measurement are as set out and defined in Schedule II, and the symbols and abbreviations therefore are as added pursuant to subparagraph 6(1)(b)(ii).
  10. ^ a b "Guidance Note on the use of Metric Units of Measurement by the Public Sector" (PDF). UK: Department for Business Innovation and Skills. 2007. Archived from the original (PDF) on 4 July 2011. Retrieved 12 December 2014.
  11. ^ "The Traffic Signs Regulations and General Directions 2002 - No. 3113 - Schedule 2 - Regulatory Signs". UK: The National Archives. 2002. Retrieved 25 April 2013.
  12. Otto GmbH
    . Retrieved 28 December 2023.
  13. ^ Flatchet, E; Petiet, J (1849). The student's guide to the locomotive engine. John Williams and Co. p. xi. One Metre is equal to ... 30.371 inches"
  14. ^ Parkinson, A C (1967). Intermediate Engineering Drawing (sixth ed.). p. 11. The basic major dia is actually 1.309 in.
  15. ^ "Climate Data Online – definition of rainfall statistics". Australia: Bureau of Meteorology. Retrieved 10 June 2012.
  16. ^ "Of Human Understanding", The Works of John Locke Esq., Vol. I, London: John Churchill, 1714, p. 293.
  17. ISBN 978-90-04-12524-7
    .
  18. ^ Wilkins, David (1871). Councils and Ecclesiastical Documents Relating to Great Britain and Ireland: English church during the Anglo-Saxon period: A.D. 595-1066. Oxford, UK: Clarendon Press. p. 48. Retrieved 18 December 2014.
  19. ISBN 978-0-87154-219-9
    .
  20. ^
    ISBN 9780671215651
    .
  21. ISBN 978-0-7509-1685-1
    .
  22. ^ Williams, John (1867). "The civil arts – mensuration". The Traditionary Annals of the Cymry. Tenby, UK: R. Mason. pp. 243–245.
  23. ^ Swinton, John (1789). A proposal for uniformity of weights and measures in Scotland. printed for Peter Hill. p. 134.
  24. ISBN 978-0-521-02709-0
    .
  25. ^ a b Butler, Charles (1814). An Easy Introduction to the Mathematics. Oxford, UK: Bartlett and Newman. pp. 61.
  26. ^ Bouvier, John (1843). "Barleycorn". A Law Dictionary: With References to the Civil and Other Systems of Foreign Law. Philadelphia, US: T. & J. W. Johnson. p. 188.
  27. ^ Long, George (1842). "Weights & Measures, Standard". The Penny Cyclopædia of the Society for the Diffusion of Useful Knowledge. London, UK: Charles Knight & Co. p. 436.
  28. ^ Judson, Lewis V (October 1963). Weights and Measures Standards of the United States - a brief history - NBS publication 447. United States Department of Commerce. p. 10–11.
  29. ^ T. C. Mendenhall, Superintendent of Standard Weights and Measures (5 April 1893). "Appendix 6 to the Report for 1893 of the Coast and Geodetic Survey" (PDF). Archived from the original (PDF) on 30 September 2012.
  30. ^ a b "The History of Gauge Blocks" (PDF). mitutoyo.com. Mitutoyo Corporation. 2013. p. 8. Retrieved 1 February 2020.
  31. ^ Gaillard, John (October 1943). Industrial Standardization and Commercial Standards Monthly. p. 293. Retrieved 1 February 2020.
  32. LCCN 65-62472
    .
  33. ^ Lewis, Herbert B. (1936). The Viewpoint of industry concerned with interchangeable manufacturing toward the proposal to standardize the inch. National Twenty-Eight Conference on Weights and Measures. US: National Bureau of Standards. p. 4. Retrieved 2 August 2012.
  34. ISBN 978-0-7844-0070-8
    .
  35. doi:10.1139/p59-014
    .
  36. ^ National Conference on Weights and Measures; United States. Bureau of Standards; National Institute of Standards and Technology (US) (1957). Report of the ... National Conference on Weights and Measures. US Department of Commerce, Bureau of Standards. pp. 45–6.
  37. ^ Astin, A.V.; Karo, H. A.; Mueller, F.H. (25 June 1959). "Refinement of Values for the Yard and the Pound" (PDF). US Federal Register.
  38. ^ United States. National Bureau of Standards (1959). Research Highlights of the National Bureau of Standards. US Department of Commerce, National Bureau of Standards. p. 13.
  39. ^ Lewis Van Hagen Judson; United States. National Bureau of Standards (1976). Weights and measures standards of the United States: a brief history. Dept. of Commerce, National Bureau of Standards : for sale by the Supt. of Docs., U.S. Govt. Print. Off. pp. 30–1. Retrieved 16 September 2012.
  40. ^ Statutory Rule No. 142.
  41. ^ Australian Government ComLaw Weights and Measures (National Standards) Regulations - C2004L00578
  42. ^ Weights and Measures Act of 1963.
  43. ^ "Thoburn v Sunderland City Council [2002] EWHC 195 (Admin)". England and Wales High Court. 18 February 2002 – via British and Irish Legal Information Institute.
  44. ^ "On what basis is one inch exactly equal to 25.4 mm? Has the imperial inch been adjusted to give this exact fit and if so when?". National Physical Laboratory. 25 March 2010. Archived from the original on 26 January 2013. Retrieved 5 April 2013.
  45. ^ a b 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)
  46. ^ Materese, Robin (26 July 2019). "U.S. Survey Foot". NIST. Retrieved 1 February 2020.
  47. ^ *de Gelder, Jacob (1824). Allereerste Gronden der Cijferkunst [Introduction to Numeracy] (in Dutch). The Hague: de Gebroeders van Cleef. p. 166. Retrieved 10 April 2022.
  48. ^ "Dictionary of the Scots Language". Edinburgh: Scottish Language Dictionaries. Retrieved 22 January 2020.

Bibliography

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