Wikipedia

Inch

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

Theinch(symbol:inor″) is aunitoflengthin theBritish Imperialand theUnited States customarysystems of measurement.It is equal to⁠1/36⁠yardor⁠1/12⁠of afoot.Derived from theRoman uncia( "twelfth" ), the wordinchis also sometimes used to translate similar units in other measurement systems,usually understood as derivingfrom the width of the human thumb.

Inch
Ameasuring tapewith inches
General information
Unit systemImperial/USunits
Unit ofLength
Symbolin, ″ (thedouble prime)[1]
Conversions
1 inin...... is equal to...
Imperial/US units⁠1/36⁠ydor⁠1/12⁠ft
Metric(SI) units25.4mm
A fire hydrant marked as 3-inch

Standards for the exact length of an inch have varied in the past, but since the adoption of theinternational yardduring the 1950s and 1960s the inch has been based on themetric systemand defined as exactly 25.4mm.

Name

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The English word "inch" (Old English:ynce) was an early borrowing fromLatinuncia( "one-twelfth;Roman inch;Roman ounce").[2]The vowel change from Latin/u/to Old English/y/(which became Modern English/ɪ/) is known asumlaut.[citation needed]The consonant change from the Latin/k/(spelledc) to English/tʃ/ispalatalisation.Both were features ofOld English phonology;seePhonological history of Old English § PalatalizationandGermanic umlaut § I-mutation in Old Englishfor more information.

"Inch" is cognate with "ounce"(Old English:ynse), whose separate pronunciation and spelling reflect its reborrowing inMiddle EnglishfromAnglo-Normanunceandounce.[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[4]). In theDutch languagea term for inch isengelse duim(english thumb).[5][6]Examples includeCatalan:polzada( "inch" ) andpolze( "thumb" );Czech:palec( "thumb" ); Danish andNorwegian:tomme( "inch" )tommel( "thumb" );Dutch:duim(whenceAfrikaans:duimandRussian:дюйм);French:pouce;Georgian:დუიმი,Hungarian:hüvelyk;Italian:pollice;Portuguese:polegada( "inch" ) andpolegar( "thumb" ); ( "duim" );Slovak:palec( "thumb" );Spanish:pulgada( "inch" ) andpulgar( "thumb" ); andSwedish:tum( "inch" ) andtumme( "thumb" ).

Usage

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Imperial or hybrid countries

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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

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Inches are used for display screens (e.g.televisionsand computer monitors) worldwide. It is the officialJapanese standardfor electronic parts, especially display screens, and is the industry standard throughout continental Europe for display screens (Germanybeing 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 intyre codes.[citation needed]

SI countries

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Both inch-based and millimeter-basedhex keysare widely available for sale in Europe.[13][14]

Technical details

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The international standard symbol for inch isin(seeISO 31-1,Annex A) but traditionally the inch is denoted by adouble prime,which is often approximated by adouble quotesymbol, and thefootby aprime,which is often approximated by anapostrophe.For example;three feet, two inchescan be written as 3′2″. (This is akin to how thefirstandsecond"cuts" of thehourare likewise indicated by prime and double prime symbols, and also thefirstandsecondcuts of thedegree.)

Subdivisions of an inch are typically written usingdyadic fractionswith odd number numerators; for example,two and three-eighths of an inchwould be written as⁠2+3/8⁠″ and not as 2.375″ nor as⁠2+6/16⁠″. However, for engineering purposes fractions are commonly given to three or four places of decimals and have been for many years.[15][16]

Equivalents

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1international inch is equal to:

History

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

The earliest known reference to the inch in England is from theLaws of Æthelberhtdating to the early 7th century, surviving in a single manuscript, theTextus Roffensisfrom 1120.[19]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 thebarleycorn.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.[22]One of the earliest such definitions is that of 1324, where the legal definition of the inch was set out in a statute ofEdward II of England,defining it as "three grains ofbarley,dry and round, placed end to end, lengthwise ".[22]

Similar definitions are recorded in both English and Welsh medieval law tracts.[23]One, dating from the first half of the 10th century, is contained in the Laws ofHywel Ddawhich superseded those ofDyfnwal,an even earlier definition of the inch in Wales. Both definitions, as recorded inAncient Laws and Institutes of Wales(vol i., pp. 184, 187, 189), are that "three lengths of a barleycorn is the inch".[24]

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.[25]However, the oldest surviving manuscripts date from the early 14th century and appear to have been altered with the inclusion of newer material.[26]

In 1814, Charles Butler, a mathematics teacher atCheam 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.[27]John Bouviersimilarly recorded in his 1843 law dictionary that the barleycorn was the fundamental measure.[28]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,andthatwas the legal definition of the inch.[27]

This was a point also made by George Long in his 1842Penny 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.[29]

Before the adoption of theinternational yard and pound,various definitions were in use. In the United Kingdom and most countries of theBritish Commonwealth,the inch was defined in terms of theImperial Standard Yard.The United States adopted the conversion factor 1 metre = 39.37 inches by an act in 1866.[30]In 1893,Mendenhall orderedthe physical realization of the inch to be based on the international prototype metres numbers 21 and 27, which had been received from theCGPM,together with the previously adopted conversion factor.[31]

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). WhenCarl Edvard Johanssonstarted manufacturinggauge blocksin 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 thede factostandard for manufacturers internationally,[32][33]with other manufacturers of gauge blocks following Johansson's definition by producing blocks designed to be equivalent to his.[34]

In 1930, theBritish Standards Institutionadopted an inch of exactly 25.4 mm. TheAmerican Standards Associationfollowed suit in 1933. By 1935, industry in 16 countries had adopted the "industrial inch" as it came to be known,[35][36]effectively endorsing Johansson's pragmatic choice of conversion ratio.[32]

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;[37][38]the United States on 1 July 1959;[39][40][41]Australia in 1961,[42]effective 1 January 1964;[43]and the United Kingdom in 1963,[44]effective on 1 January 1964.[45]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.[46][47]

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US survey inches

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The United States retained the⁠1/39.37⁠-metre definition for surveying, producing a 2 millionth part difference between standard andUS surveyinches.[47]This is approximately⁠1/8⁠inch per mile; 12.7 kilometres is exactly500,000standard inches and exactly499,999survey inches. This difference is substantial when doing calculations inState Plane Coordinate Systemswith coordinate values in the hundreds of thousands or millions of feet.

In 2020, theNational Institute of Standards and Technologyannounced 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.[48]This implies that the survey inch was replaced by the international inch.

Continental inches

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Main articles:Roman inchandFrench inch

Before the adoption of the metric system, several European countries had customary units whose name translates into "inch". The Frenchpoucemeasured roughly 27.0 mm, at least when applied to describe the calibre of artillerypieces.TheAmsterdam foot(voet) consisted of 11 Amsterdam inches (duim). The Amsterdam foot is about 8% shorter than an English foot.[49]

Scottish inch

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The now obsoleteScottish inch(Scottish Gaelic:òirleach),⁠1/12⁠of a Scottish foot, was about 1.0016 imperial inches (about 25.44 mm).[50]

See also

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Notes

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  1. ^A tenth of athou,used inmachining.
  2. ^Used inmachiningandpapermaking.
  3. ^Formerly used inAmerican Englishbut now often avoided to prevent confusion withmillimetres.
  4. ^Used by the AustralianBureau of Meteorologyfor measuring rainfall until 1973[17]
  5. ^abPart ofJohn Locke's proposal for decimalization of English measures[18]
  6. ^The typographic point was originally⁠1/9⁠of the height of a (capital) letter (cap height) but later acquired a number of different absolute definitions; seePoint (typography) § Historyfor details.
  7. ^Used ingunmaking.
  8. ^Used inbotany.
  9. ^Used inbuttonmanufacturing.
  10. ^Used intypography.
  11. ^Used in American and Britishshoe sizes.
  12. ^Used in measuring the height ofhorses.
  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 fromAttenborough 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.[20][21]

References

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Citations

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  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.Retrieved28 March2019.
  5. ^"duim - lengtemaat".Genootschap Onze Taal.Retrieved22 October2022.
  6. ^"duim".24 May 2020.Retrieved22 October2022.
  7. ^"Corpus of Contemporary American English".Brigham Young University.US.Retrieved5 December2011.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.Retrieved11 January2018– via Justice Laws Website.
  9. ^"Weights and Measures Act".Canada. 1 August 2014. p. 2.Retrieved18 December2014– 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. ^ab"Guidance Note on the use of Metric Units of Measurement by the Public Sector"(PDF).UK: Department for Business Innovation and Skills. 2007. Archived fromthe original(PDF)on 4 July 2011.Retrieved12 December2014.
  11. ^"The Traffic Signs Regulations and General Directions 2002 - No. 3113 - Schedule 2 - Regulatory Signs".UK: The National Archives. 2002.Retrieved25 April2013.
  12. ^"Fernseher"(in German).Otto GmbH.Retrieved28 December2023.
  13. ^"Nyckelsats tum Cocraft, 9 delar"(in Swedish).Clas OhlsonSweden.Retrieved28 December2023.
  14. ^"Nyckelsats mm Cocraft, 9 delar"(in Swedish).Clas OhlsonSweden.Retrieved28 December2023.
  15. ^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 "
  16. ^Parkinson, A C (1967).Intermediate Engineering Drawing(sixth ed.). p. 11.The basic major dia is actually 1.309 in.
  17. ^"Climate Data Online – definition of rainfall statistics".Australia:Bureau of Meteorology.Retrieved10 June2012.
  18. ^"Of Human Understanding",The Works of John Locke Esq.,Vol. I,London: John Churchill, 1714, p.293.
  19. ^Goetz, Hans-Werner; Jarnut, Jörg;Pohl, Walter(2003).Regna and Gentes: The Relationship Between Late Antique and Early Medieval Peoples and Kingdoms in the Transformation of the Roman World.BRILL. p. 33.ISBN978-90-04-12524-7.
  20. ^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.Retrieved18 December2014.
  21. ^Duncan, Otis Dudley(1984).Notes on social measurement: historical and critical.US: Russell Sage Foundation. p. 87.ISBN978-0-87154-219-9.
  22. ^abKlein, H. Arthur (1974).The world of measurements: masterpieces, mysteries and muddles of metrology.New York, US: Simon and Schuster.ISBN9780671215651.
  23. ^Hawkes, Jane; Mills, Susan (1999).Northumbria's Golden Age.UK: Sutton. p. 310.ISBN978-0-7509-1685-1.
  24. ^Williams, John (1867). "The civil arts – mensuration".The Traditionary Annals of the Cymry.Tenby, UK: R. Mason. pp.243–245.
  25. ^Swinton, John(1789).A proposal for uniformity of weights and measures in Scotland.printed for Peter Hill. p. 134.
  26. ^Gemmill, Elizabeth; Mayhew, Nicholas (22 June 2006).Changing Values in Medieval Scotland: A Study of Prices, Money, and Weights and Measures.UK: Cambridge University Press. p. 113.ISBN978-0-521-02709-0.
  27. ^abButler, Charles (1814).An Easy Introduction to the Mathematics.Oxford, UK: Bartlett and Newman. pp.61.
  28. ^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.
  29. ^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.
  30. ^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.
  31. ^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 fromthe original(PDF)on 30 September 2012.
  32. ^ab"The History of Gauge Blocks"(PDF).mitutoyo.Mitutoyo Corporation. 2013. p. 8.Retrieved1 February2020.
  33. ^Gaillard, John (October 1943).Industrial Standardization and Commercial Standards Monthly.p. 293.Retrieved1 February2020.
  34. ^Cochrane, Rexmond C. (1966).Measures for Progress. NIST Special Publication, isue 275.U.S. Government Printing Office. p. 200.LCCN65-62472.
  35. ^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.Retrieved2 August2012.
  36. ^Wandmacher, Cornelius; Johnson, Arnold Ivan (1995).Metric Units in Engineering--going SI: How to Use the International Systems of Measurement Units (SI) to Solve Standard Engineering Problems.ASCE Publications. p. 265.ISBN978-0-7844-0070-8.
  37. ^Howlett, L. E. (1 January 1959). "Announcement on the International Yard and Pound".Canadian Journal of Physics.37(1): 84.Bibcode:1959CaJPh..37...84H.doi:10.1139/p59-014.
  38. ^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.
  39. ^Astin, A.V.; Karo, H. A.; Mueller, F.H. (25 June 1959)."Refinement of Values for the Yard and the Pound"(PDF).USFederal Register.
  40. ^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.
  41. ^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.Retrieved16 September2012.
  42. ^Statutory Rule No. 142.
  43. ^Australian Government ComLawWeights and Measures (National Standards) Regulations - C2004L00578
  44. ^Weights and Measures Act of 1963.
  45. ^"Thoburn v Sunderland City Council [2002] EWHC 195 (Admin)".England and Wales High Court. 18 February 2002 – via British and Irish Legal Information Institute.
  46. ^"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 fromthe originalon 26 January 2013.Retrieved5 April2013.
  47. ^abA. 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)
  48. ^Materese, Robin (26 July 2019)."U.S. Survey Foot".NIST.Retrieved1 February2020.
  49. ^*de Gelder, Jacob (1824).Allereerste Gronden der Cijferkunst[Introduction to Numeracy] (in Dutch). The Hague: de Gebroeders van Cleef. p. 166.Retrieved10 April2022.
  50. ^"Dictionary of the Scots Language".Edinburgh: Scottish Language Dictionaries.Retrieved22 January2020.

Bibliography

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