Foot (unit) explained

foot
Symbol:	ft
Symbol2:	′
Standard:	Imperial/US units
Quantity:	Length
Units2:	Metric (SI) units
Units1:	Imperial/US units

The foot (standard symbol: ft)^[1] is a unit of length in the British imperial and United States customary systems of measurement. The prime symbol,, is commonly used to represent the foot.^[2] In both customary and imperial units, one foot comprises 12 inches, and one yard comprises three feet. Since an international agreement in 1959, the foot is defined as equal to exactly 0.3048 meters.

Historically, the "foot" was a part of many local systems of units, including the Greek, Roman, Chinese, French, and English systems. It varied in length from country to country, from city to city, and sometimes from trade to trade. Its length was usually between 250 mm and 335 mm and was generally, but not always, subdivided into 12 inches or 16 digits.

The United States is the only industrialized country that uses the (international) foot in preference to the meter in its commercial, engineering, and standards activities.^[3] The foot is legally recognized in the United Kingdom; road distance signs must use imperial units (however, distances on road signs are always marked in miles or yards, not feet; bridge clearances are given in meters as well as feet and inches), while its usage is widespread among the British public as a measurement of height.^{[4] [5]} The foot is recognized as an alternative expression of length in Canada.^[6] Both the UK and Canada have partially metricated their units of measurement. The measurement of altitude in international aviation (the flight level unit) is one of the few areas where the foot is used outside the English-speaking world.

The most common plural of foot is feet. However, the singular form may be used like a plural when it is preceded by a number, as in "he is six foot tall."^[7]

Historical origin

See also: pous. Historically, the human body has been used to provide the basis for units of length.^[8] The foot of an adult European-American male is typically about 15.3% of his height,^[9] giving a person of 175cm (69inches) a foot-length of about 268mm, on average.

Archaeologists believe that, in the past, the people of Egypt, India, and Mesopotamia preferred the cubit, while the people of Rome, Greece, and China preferred the foot. Under the Harappan linear measures, Indus cities during the Bronze Age used a foot of 13.2inches and a cubit of 20.8inches.^[10] The Egyptian equivalent of the foot—a measure of four palms or 16 digits—was known as the Egyptian (Ancient);: djeser and has been reconstructed as about 30cm (10inches).

The Greek foot (Greek, Ancient (to 1453);: πούς, Greek, Ancient (to 1453);: pous) had a length of of a stadion,^[11] one stadion being about 181.2m (594.5feet);^[12] therefore a foot was, at the time, about 302mm. Its exact size varied from city to city and could range between 270mm and 350mm, but lengths used for temple construction appear to have been about 295mm to 325mm; the former was close to the size of the Roman foot.

The standard Roman foot (Latin: pes) was normally about 295.7mm (97% of today's measurement),^[13] but in some provinces, particularly Germania Inferior, the so-called Latin: pes Drusianus (foot of Nero Claudius Drusus) was sometimes used, with a length of about 334mm. (In reality, this foot predated Drusus.)^{[14] [15]}

Originally both the Greeks and the Romans subdivided the foot into 16 digits, but in later years, the Romans also subdivided the foot into 12 Latin: unciae (from which both the English words "inch" and "ounce" are derived).

After the fall of the Roman Empire, some Roman traditions were continued but others fell into disuse. In AD 790 Charlemagne attempted to reform the units of measure in his domains. His units of length were based on the French: [[toise]] and in particular the French: toise de l'Écritoire, the distance between the fingertips of the outstretched arms of a man.^[16] The French: toise has 6 French: pieds (feet) each of 326.6mm.

He was unsuccessful in introducing a standard unit of length throughout his realm: an analysis of the measurements of Charlieu Abbey shows that during the 9th century the Roman foot of 296.1mm was used; when it was rebuilt in the 10th century, a foot of about 320mm^[17] was used. At the same time, monastic buildings used the Carolingian foot of 340mm.^{[17] [18]}

The procedure for verification of the foot as described in the 16th century posthumously published work by Jacob Köbel in his book German: Geometrei. Von künstlichem Feldmessen und absehen is:^{[19] [20]}

England

See also: Yard.

The Neolithic long foot, first proposed by archeologists Mike Parker Pearson and Andrew Chamberlain, is based upon calculations from surveys of Phase 1 elements at Stonehenge. They found that the underlying diameters of the stone circles had been consistently laid out using multiples of a base unit amounting to 30 long feet, which they calculated to be 1.056 of a modern international foot (thus 12.672 inches or 0.3219 m). Furthermore, this unit is identifiable in the dimensions of some stone lintels at the site and in the diameter of the "southern circle" at nearby Durrington Walls. Evidence that this unit was in widespread use across southern Britain is available from the Folkton Drums from Yorkshire (neolithic artifacts, made from chalk, with circumferences that exactly divide as integers into ten long feet) and a similar object, the Lavant drum, excavated at Lavant, Sussex, again with a circumference divisible as a whole number into ten long feet.^[21]

The measures of Iron Age Britain are uncertain and proposed reconstructions such as the Megalithic Yard are controversial. Later Welsh legend credited Dyfnwal Moelmud with the establishment of their units, including a foot of 9 inches. The Belgic or North German foot of 335mm was introduced to England either by the Belgic Celts during their invasions prior to the Romans or by the Anglo-Saxons in the 5th and 6th century.

Roman units were introduced following their invasion in AD 43. Following the Roman withdrawal and Saxon invasions, the Roman foot continued to be used in the construction crafts while the Belgic foot was used for land measurement. Both the Welsh and Belgic feet seem to have been based on multiples of the barleycorn, but by as early as 950 the English kings seem to have (ineffectually) ordered measures to be based upon an iron yardstick at Winchester and then London. Henry I was said to have ordered a new standard to be based upon the length of his own arm and, by the Act concerning the Composition of Yards and Perches^[22] traditionally credited to Edward I or II, the statute foot was a different measure, exactly of the old (Belgic) foot. The barleycorn, inch, ell, and yard were likewise shrunk, while rods and furlongs remained the same.^[23] The ambiguity over the state of the mile was resolved by the 1593 Act against Converting of Great Houses into Several Tenements and for Restraint of Inmates and Inclosures in and near about the City of London and Westminster, which codified the statute mile as comprising 5,280 feet. The differences among the various physical standard yards around the world, revealed by increasingly powerful microscopes, eventually led to the 1959 adoption of the international foot defined in terms of the meter.

Definition

International foot

The international yard and pound agreement of July 1959 defined the length of the international yard in the United States and countries of the Commonwealth of Nations as exactly 0.9144 meters. Consequently, since a foot is one third of a yard, the international foot is defined to be equal to exactly 0.3048 meters. This was 2 ppm shorter than the previous US definition and 1.7 ppm longer than the previous British definition.^[24]

The 1959 agreement concluded a series of step-by-step events, set off in particular by the British Standards Institution's adoption of a scientific standard inch of 25.4 millimeters in 1930.

Symbol

The IEEE standard symbol for a foot is "ft".^[25] In some cases, the foot is denoted by a prime, often approximated by an apostrophe, and the inch by a double prime; for example, 2feet 4 inches is sometimes denoted 2′4″.^[26]

Imperial units

In Imperial units, the foot was defined as  yard, with the yard being realized as a physical standard (separate from the standard meter). The yard standards of the different Commonwealth countries were periodically compared with one another.^[27] The value of the United Kingdom primary standard of the yard was determined in terms of the meter by the National Physical Laboratory in 1964 to be,^[28] implying a pre-1959 UK foot of .

The UK adopted the international yard for all purposes through the Weights and Measures Act 1963, effective January 1, 1964.^[29]

Survey foot

When the international foot was defined in 1959, a great deal of survey data was already available based on the former definitions, especially in the United States and in India. The small difference between the survey foot and the international foot would not be detectable on a survey of a small parcel, but becomes significant for mapping, or when the state plane coordinate system (SPCS) is used in the US, because the origin of the system may be hundreds of thousands of feet (hundreds of miles) from the point of interest. Hence the previous definitions continued to be used for surveying in the United States and India for many years, and are denoted survey feet to distinguish them from the international foot. The United Kingdom was unaffected by this problem, as the retriangulation of Great Britain (1936–62) had been done in meters.

US survey foot

In the United States, the foot was defined as 12 inches, with the inch being defined by the Mendenhall Order of 1893 via 39.37 inches = 1 m (making a US foot exactly meters, approximately).^[30]

On December 31, 2022, the National Institute of Standards and Technology, the National Geodetic Survey, and the United States Department of Commerce deprecated use of the US survey foot and recommended conversion to either the meter or the international foot (0.3048 m).^{[31] [32] [33]} However, the historic relevance of the US survey foot persists, as the Federal Register notes:^[34]

State legislation is also important for determining the conversion factor to be used for everyday land surveying and real estate transactions, although the difference (two parts per million) is of no practical significance given the precision of normal surveying measurements over short distances (usually much less than a mile). Out of 50 states and six other jurisdictions, 40 have legislated that surveying measures should be based on the US survey foot, six have legislated that they be made on the basis of the international foot, and ten have not specified.^[35]

Indian survey foot

The Indian survey foot is defined as exactly,^[36] presumably derived from a measurement of the previous Indian standard of the yard. The current National Topographic Database of the Survey of India is based on the metric WGS-84 datum,^[37] which is also used by the Global Positioning System.

Historical use

Metric foot

An ISO 2848 measure of 3 basic modules (30 cm) is called a "metric foot", but there were earlier distinct definitions of a metric foot during metrication in France and Germany.

France

In 1799 the meter became the official unit of length in France. This was not fully enforced, and in 1812 Napoleon introduced the system of mesures usuelles which restored the traditional French measurements in the retail trade, but redefined them in terms of metric units. The foot, or pied métrique, was defined as one third of a meter. This unit continued in use until 1837.^[38]

Germany

In southwestern Germany in 1806, the Confederation of the Rhine was founded and three different reformed feet were defined, all of which were based on the metric system:^[39]

• In Hesse, the Fuß (foot) was redefined as 25 cm.
• In Baden, the Fuß was redefined as 30 cm.
• In the Palatinate, the Fuß was redefined as being  cm (as in France).

Other obsolete feet

Prior to the introduction of the metric system, many European cities and countries used the foot, but it varied considerably in length: the Dutch; Flemish: voet in Ypres, Belgium, was 273.8 millimeters (10.78in) while the piede in Venice was 347.73 millimeters (13.690in). Lists of conversion factors between the various units of measure were given in many European reference works including:

• Traité, Paris – 1769^[40]
• Palaiseau – Bordeaux: 1816 ^[41]
• de Gelder, Amsterdam and The Hague – 1824^[42]
• Horace, Brussels – 1840^[43]
• Noback & Noback (2 volumes), Leipzig – 1851^{[44] [45]}
• Bruhns, Leipzig – 1881^[46]

Many of these standards were peculiar to a particular city, especially in Germany (which, before German unification in 1871, consisted of many kingdoms, principalities, free cities and so on). In many cases the length of the unit was not uniquely fixed: for example, the English foot was stated as 11 pouces 2.6 lignes (French inches and lines) by Picard, 11 pouces 3.11 lignes by Maskelyne, and 11 pouces 3 lignes by D'Alembert.^[47]

Most of the various feet in this list ceased to be used when the countries adopted the metric system. The Netherlands and modern Belgium adopted the metric system in 1817, having used the French: mesures usuelles under Napoleon^[48] and the newly formed German Empire adopted the metric system in 1871.^[49]

The palm (typically 200–280 mm, ie. 7 to 11 inches) was used in many Mediterranean cities instead of the foot. Horace Doursther, whose reference was published in Belgium which had the smallest foot measurements, grouped both units together, while J. F. G. Palaiseau devoted three chapters to units of length: one for linear measures (palms and feet); one for cloth measures (ells); and one for distances traveled (miles and leagues).

Obsolete feet details

In the table below, arbitrary cut-off points of 270 mm and 350 mm (10 to 13 inches) have been chosen.

Location	Modern country	Local name	Metric equivalent (mm)	Comments
Vienna	Austria	German: italic=no|Wiener Fuß	316.102^[50]
Tyrol	Austria	German: italic=no|Fuß	334.12
Ypres (Ieper)	Belgium	Dutch; Flemish: italic=no|voet	273.8
Bruges/Brugge	Belgium	Dutch; Flemish: italic=no|voet	274.3
Brussels	Belgium	Dutch; Flemish: italic=no|voet	275.75
Hainaut	Belgium	French: italic=no|pied	293.39
Liège	Belgium	French: italic=no|pied	294.70
Kortrijk	Belgium	Dutch; Flemish: italic=no|voet	297.6
Aalst	Belgium	Dutch; Flemish: italic=no|voet	277.2^[51]
Mechelen	Belgium	Dutch; Flemish: italic=no|voet	278.0
Leuven	Belgium	Dutch; Flemish: italic=no|voet	285.5
Tournai	Belgium	French: italic=no|pied	297.77
Antwerp	Belgium	Dutch; Flemish: italic=no|voet	286.8
China	China	tradesman's foot	338.3
China	China	mathematician's foot	333.2
China	China	builder's foot	322.8
China	China	surveyor's foot	319.5
Moravia	Czech Republic	Czech: italic=no|stopa	295.95
Prague	Czech Republic	Czech: italic=no|stopa	296.4	(1851) Bohemian foot or shoe
			301.7	(1759) Quoted as "11 French: pouces French: lignes"
Denmark	Denmark	Danish: italic=no|fod	313.85	Until 1835, thereafter the Prussian foot
			330.5	(1759) Quoted as " French: lignes larger than the French: pied [of Paris]"
France	France	French: italic=no|pied du roi	324.84^[52]	^[53]
Angoulême	France	French: italic=no|pied d'Angoulême	347.008^[54]
Bordeaux (urban)	France	French: italic=no|pied de ville de Bordeaux	343.606
Bordeaux (rural)	France	French: italic=no|pied de terre de Bordeaux	357.214
Strasbourg	France	French: italic=no|pied de Strasbourg	294.95
Württemberg	Germany	German: italic=no|Fuß	286.49
Hanover	Germany	German: italic=no|Fuß	292.10
Augsburg	Germany	German: italic=no|römischer Fuß	296.17
Nuremberg	Germany	German: italic=no|Fuß	303.75
Meiningen-Hildburghausen	Germany	German: italic=no|Fuß	303.95
Oldenburg	Germany	German: italic=no|römischer Fuß	296.41
Weimar	Germany	German: italic=no|Fuß	281.98
Lübeck	Germany	German: italic=no|Fuß	287.62
Aschaffenburg	Germany	German: italic=no|Fuß	287.5
Darmstadt	Germany	German: italic=no|Fuß	287.6	Until 1818, thereafter the Hessen "metric foot"
Bremen	Germany	German: italic=no|Fuß	289.35
Rhineland	Germany	German: italic=no|Fuß	313.7
Berlin	Germany	German: italic=no|Fuß	309.6
Hamburg	Germany	German: italic=no|Fuß	286.8
Bavaria	Germany	German: italic=no|Fuß	291.86
Aachen	Germany	German: italic=no|Fuß	282.1
Leipzig	Germany	German: italic=no|Fuß	282.67
Dresden	Germany	German: italic=no|Fuß	283.11
Saxony	Germany	German: italic=no|Fuß	283.19
Prussia	Germany, Poland, Russia etc.	German: italic=no|Rheinfuß	313.85
Frankfurt am Main	Germany	German: italic=no|Fuß	284.61
Venice & Lombardy	Italy		347.73
Turin	Italy		323.1
Rome	Italy	Italian: italic=no|piede romano	297.896
Riga	Latvia	Latvian: italic=no|pēda	274.1
Malta	Malta	italic=no|pied	283.7
Utrecht	Netherlands	Dutch; Flemish: italic=no|voet	272.8^[55]
Amsterdam	Netherlands	Dutch; Flemish: italic=no|voet	283.133	Divided into 11 Dutch; Flemish: duimen (inches,)
	Netherlands	Dutch; Flemish: italic=no|voet	285.0
's-Hertogenbosch	Netherlands	Dutch; Flemish: italic=no|voet	287.0
Gelderland	Netherlands	Dutch; Flemish: italic=no|voet	292.0
Bloois (Zeeland)	Netherlands	Dutch; Flemish: italic=no|voet	301.0
Schouw	Netherlands	Dutch; Flemish: italic=no|voet	311.0
Rotterdam	Netherlands	Dutch; Flemish: italic=no|voet	312.43
Rijnland	Netherlands	Dutch; Flemish: italic=no|voet	314.858
Norway	Norway	Norwegian: italic=no|fot	313.75^[56]	(1824–1835)^[57] Thereafter as for Sweden.
Warsaw	Poland	Polish: italic=no|stopa	297.8^[58]	Until 1819
			288.0	(From 1819) Polish Polish: italic=no|stopa
Lisbon	Portugal	Portuguese: italic=no|pé	330.0	(From 1835)^[59]
South Africa	South Africa	Cape foot	314.858^[60]	Originally equal to the Rijnland foot; redefined as 1.033 English feet in 1859.
Burgos and Castile	Spain	Spanish; Castilian: italic=no|pie de Burgos/<br />Castellano	278.6	(1759) Quoted as "122.43 French: lignes"
Toledo	Spain	Spanish; Castilian: italic=no|pie	279.0	(1759) Quoted as "10 French: pouces 3.7 French: lignes"^[61]
Sweden	Sweden	Swedish: italic=no|fot	296.9	= 12 Swedish: tum (inches). The Swedish Swedish: fot was also used in Finland (Finnish: jalka).
Zürich	Switzerland		300.0
Galicia	Ukraine, Poland	Polish: italic=no|stopa galicyjska	296.96	Part of Austria–Hungary before World War I
Scotland	United Kingdom		305.287^[62]	^[63]

In Belgium, the words French: pied (French) and Dutch; Flemish: voet (Dutch) would have been used interchangeably.

Notes

1. Book: BS350:Part 1:1974 Conversion factors and tables Part 1. Basis of tables. Conversion factors . 1974 . British Standards Institution . 5, 91.
2. Book: Chicago Manual of Style . 17th . 2017 . University of Chicago Press . ¶ 10.66.
3. Book: https://www.cia.gov/library/publications/the-world-factbook/appendix/appendix-g.html . The World Factbook . January 17, 2007 . . Appendix G – Weights and Measures . February 4, 2007 . live . http://archive.wikiwix.com/cache/20110223164402/https://www.cia.gov/library/publications/the-world-factbook/appendix/appendix-g.html . February 23, 2011 .
4. News: Will British people ever think in metric?. BBC. December 21, 2011. Jon. Kelly. live. https://web.archive.org/web/20120424232814/http://www.bbc.co.uk/news/magazine-16245391. April 24, 2012.
5. Alder, Ken (2002). The Measure of all Things—The Seven-Year-Odyssey that Transformed the World. London: Abacus.
6. Weights and Measures Act, accessed January 2012, Act current to January 18, 2012. Basis for units of measurement 4.(1) All units of measurement used in Canada shall be determined on the basis of the International System of Units established by the General Conference of Weights and Measures. (...) 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).
7. Encyclopedia: foot, noun . Oxford English Dictionary . Oxford University Press . June 13, 2024 .
8. Book: Oswald Ashton Wentworth Dilke. Oswald A.W. Dilke. Mathematics and measurement. February 2, 2012. May 22, 1987. University of California Press. 978-0-520-06072-2. 23.
9. Sexual dimorphism in foot length proportionate to stature . Daniel M . Fessler . Kevin J . Haley . Roshni D . Lal . Annals of Human Biology . January–February 2005 . 32 . 1 . 44–59 . 10.1080/03014460400027581 . 15788354 . 194735 . dead . https://web.archive.org/web/20110608084140/http://www.sscnet.ucla.edu/anthro/faculty/fessler/pubs/AHBFootSizeDimorphism.pdf . June 8, 2011. mdy-all.
10. Kenoyer JM (2010) "Measuring the Harappan world," in Morley I & Renfrew C (edd) The Archaeology of Measurement, 117; Web site: Archived copy . January 11, 2015 . dead . https://web.archive.org/web/20150626134828/http://a.harappa.com/sites/g/files/g65461/f/Kenoyer%202010%20Measuring%20the%20Harappan%20World.pdf . June 26, 2015 .
11. Web site: History of Herodotus : a new English version. Herodotus. George. Rawlinson. May 14, 1861. New York D. Appleton. Internet Archive.
12. Web site: Epidauros, Stadium (Building). www.perseus.tufts.edu. live. https://web.archive.org/web/20170510073158/http://www.perseus.tufts.edu/hopper/artifact?name=Epidauros%2C+Stadium&object=Building. May 10, 2017.
13. Hosch, William L. (ed.) (2010) The Britannica Guide to Numbers and Measurement New York, NY: Britannica Educational Publications, 1st edition., p.206
14. Book: Oswald Ashton Wentworth Dilke. Oswald A.W. Dilke. Mathematics and measurement. February 2, 2012. May 22, 1987. University of California Press. 978-0-520-06072-2. 26.
15. Duncan-Jones . R. P. . 1980 . Length-Units in Roman Town Planning: The Pes Monetalis and the Pes Drusianus . Britannia . 11 . 127–133 . 10.2307/525675. 525675 . 164149478 .
16. Web site: How Many? A Dictionary of Units of Measurement . Russ Rowlett . . February 28, 2011. live . https://web.archive.org/web/20121224005450/http://www.unc.edu/~rowlett/units/dictT.html . December 24, 2012. mdy-all.
17. The original reference was given in a round number of centimeters.
18. 987740. Elizabeth R. Sutherland. Journal of the Society of Architectural Historians. Feet and dates at Charlieu. May 1957. 16. 2. 2–5. 10.2307/987740.
19. Book: Geometrei. Von künstlichem Feldmessen und absehen . 1535 . Jacob Koebel . de . live . https://web.archive.org/web/20111116021207/http://www.robweir.com/blog/2007/12/right-and-lawful-rood.html . November 16, 2011. mdy-all . Jacob Koebel.
20. Web site: Geometrey . digital.slub-dresden.de . Saxon State Library . February 22, 2019 . de-DE.
21. Teather . Anne . etal. Getting the Measure of Stonehenge . . February 8, 2019 . 165 . 48–51.
22. Book: Great Britain. The statutes at large: from the Magna Charta, to the end of the eleventh Parliament of Great Britain, anno 1761 (continued to 1807). November 30, 2011. 1. 1762. Printed by J. Bentham. 400.
23. Book: Zupko, Ronald Edward . Ronald Edward Zupko . British Weights and Measures: A History from Antiquity to the Seventeenth Century . University of Wisconsin Press . 1977 . 978-0-299-07340-4 . 6, 10, 20 .
24. Web site: 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? . . July 24, 2012. dead . https://web.archive.org/web/20120807195334/http://www.npl.co.uk/reference/faqs/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-(faq-length) . August 7, 2012. mdy-all.
25. Web site: Recommended Unit Symbols, SI Prefixes, and Abbreviations. April 7, 2021.
26. Book: Chicago Manual of Style . 17th . 2017 . University of Chicago Press . ¶ 10.66.
27. See, for example, Report on the Comparisons of the Parliamentary Copies of the Imperial Standards with the Imperial Standard Yard and the Imperial Standard Pound and with each other during the Years 1947 to 1948 (H.M.S.O., London, 1950). Report on the Comparisons of the Parliamentary Copies of the Imperial Standards with each other during the Year 1957 (H.M.S.O., London, 1958).
28. Bigg, P. H. . Anderton, Pamela . March 1964 . The United Kingdom standards of the yard in terms of the meter . dead . British Journal of Applied Physics . 15 . 3 . 291–300 . 10.1088/0508-3443/15/3/308 . 1964BJAP...15..291B . https://archive.today/20120803014104/http://iopscience.iop.org/0508-3443/15/3/308 . August 3, 2012 . May 16, 2009 .
29. http://www.bailii.org/ew/cases/EWHC/Admin/2002/195.html Thoburn v Sunderland City Council [2002] EWHC 195 (Admin) (18 February 2002)
30. 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 June 30, 1959)
31. Web site: U.S. Survey Foot. National Institute of Standards and Technology. 2024-04-04. 2023-01-04.
32. https://www.ngs.noaa.gov/web/news/measure-unit-change-coming.shtml "Measuring Unit Change Coming in 2022"
33. News: Mitchell. Alanna. August 18, 2020. America Has Two Feet. It's About to Lose One of Them. en-US. The New York Times. August 19, 2020. 0362-4331.
34. Web site: Deprecation of the United States (U.S.) Survey Foot . Federal Register . October 5, 2020.
35. https://www.ngs.noaa.gov/SPCS/maps.shtml#spcs83 "State Plane Coordinate System"
36. Schedule to the Standards of Weights and Measures Act, 1976.
37. [Survey of India]
38. Web site: Un historique du mètre . fr . Denis Février . Ministère de l'Économie, des Finances et de l'Industrie . March 10, 2011. live . https://web.archive.org/web/20110228185545/http://www.industrie.gouv.fr/metro/aquoisert/metre.htm . February 28, 2011. mdy-all.
39. Web site: Amtliche Maßeinheiten in Europa 1842 . de . Official measures in Europe 1842 . September 22, 2012. live . https://web.archive.org/web/20130723074500/http://www.spasslernen.de/geschichte/groessen/mas4.htm . July 23, 2013. mdy-all.
40. Book: d'Anville , Jean Baptiste Bourguignon . Traité des mesures itinéraires anciennes et modernes. fr. Treatise of ancient and modern measures of distance. 1769. Paris. de l'Imprimerie Royale. October 24, 2011 .
41. Book: Palaiseau , JFG . Métrologie universelle, ancienne et moderne: ou rapport des poids et mesures des empires, royaumes, duchés et principautés des quatre parties du monde. Bordeaux. October 1816. October 30, 2011.
42. Book: Allereerste Gronden der Cijferkunst. Jacob de Gelder. 's-Gravenhage (The Hague) and Amsterdam. nl. 1824. 163–176. de Gebroeders van Cleef. Introduction to Numeracy. March 2, 2011.
43. Book: Doursther , Horace . Dictionnaire universel des poids et mesures anciens et modernes. Brussels. M. Hayez. October 25, 2011. 1840. liege.. 402–418.
44. Book: Vollständiges tasehenbuch der Münz-, Maass- und Gewichts-Verhältnisse etc. aller Länder und Handelsplätze. de. Comprehensive pocketbook of money, weights and measures for all counties and trading centres. Christian. Noback. Friedrich Eduard. Noback. 1851. I. Leipzig. F. А. Brockhaus. October 24, 2011.
45. Book: Vollständiges tasehenbuch der Münz-, Maass- und Gewichts-Verhältnisse etc. aller Länder und Handelsplätze. de. Comprehensive pocketbook of money, weights and measures for all counties and trading centres. Christian. Noback. Friedrich Eduard. Noback. 1851. II. Leipzig. F. А. Brockhaus. October 24, 2011.
46. Book: Bruhns , Carl . new manual of logarithms to seven places of decimals. 610. Bernhard Tauchnitz. Leipzig. 1881. October 26, 2011.
47. Web site: Plan for Establishing Uniformity in the Coinage, Weights, and Measures of the United States . Thomas Jefferson . July 13, 1790. November 8, 2011 . . live . http://archive.wikiwix.com/cache/20110606150632/http://avalon.law.yale.edu/18th_century/jeffplan.asp . June 6, 2011. Thomas Jefferson.
48. Book: de Gelder , Jacob . Allereerste Gronden der Cijferkunst. The Hague and Amsterdam. nl. 1824. 155–157. De Gebroeders van Cleef. Introduction to Numeracy. March 2, 2011.
49. Web site: Metrologie . de . Andreas . Dreizler . April 20, 2009 . Technical University of Darmstadt . March 28, 2011 . etal .
50. [:File:Fußmaße1.jpg|File]
51. Web site: Maten en gewichten. nl. Weights and measures. Vlaamse Vereniging voor Familiekunde (Flemish Association for Family History). October 24, 2011. 2011. dead. https://web.archive.org/web/20120425091424/http://www.familiekunde-vlaanderen.be/maten-en-gewichten. April 25, 2012.
52. Web site: Les anciennes unités et leurs équivalences . Old units and their equivalences . fr . Le Cybergroupe Généalogique de Charente Poitevine . 2011 . February 25, 2011. live . https://web.archive.org/web/20110720204605/http://www.cgcp.asso.fr/FAQ/divers/anciennes_unites.php . July 20, 2011. mdy-all.
53. The original meter was computed using pre-metric French units.
54. Bibliothèque de l'École des chartes. De l'équivalence des anciennes mesures. A propos d'une publication récente. Values of ancient measures quoted in recent publications. fr. 1913. 74. 267–328. P. Guilhiermoz. 10.3406/bec.1913.448498.
55. Book: Rose , Joshua . Pattern Makers Assistant . D. van Nostrand Co. . 9th . 1900 . New York . 264 .
56. News: Mål, vekt og norsk selvstendighet. no. Dimensions, weight and Norwegian independence. Aftenposten. July 21, 2005. leif. halbo.
57. The Norwegian Norwegian: fot was defined in 1824 as the length of a (theoretical) pendulum that would have a period of  seconds at 45° from the equator.
58. – Information copied from
59. Prior to 1835, the Portuguese: pé or foot was not used in Portugal; instead a palm was used. In 1835 the size of the palm was increased from 217.37 mm (according to Palaiseau) to 220 mm.
60. Web site: The Cape Geodetic Standards and Their Impact on Africa . Tomasz Zakiewicz . FIG . Cairo . April 2005 . January 4, 2012. live . https://web.archive.org/web/20120120235610/http://www.fig.net/pub/cairo/papers/wshs_03/wshs03_02_zakiewich.pdf . January 20, 2012. mdy-all.
61. The source document used pre-metric French units (French: pied, French: pouce and French: ligne).
62. Web site: Scottish Weights and Measures: Distance and Area . Scottish Archive Network . January 28, 2010. live . https://web.archive.org/web/20090814193601/http://www.scan.org.uk/measures/distance.asp . August 14, 2009. mdy-all.
63. The Scots foot ceased to be legal after the Act of Union in 1707.

Present day uses

International ISO-standard and other intermodal shipping containers

International Standards Organisation (ISO)-defined intermodal containers for efficient global freight/cargo shipping, were defined using feet rather than meters for their leading outside (corner) dimensions. All ISO-standard containers to this day are eight feet wide, and their outer heights and lengths are also primarily defined in, or derived from feet.
Quantities of global shipping containers are still primarily counted in Twenty-foot Equivalent Units, or TEUs.

Aviation

Everyday global (civilian) air traffic / aviation continues to be controlled in flight levels (flying altitudes) separated by thousands of feet (although typically read out in hundreds – e.g. flight level 330 actually means 33,000 feet, or about 10 kilometres in altitude).

Relation to shoe size

The length of the (international) foot corresponds to a human foot with shoe size of 13 (UK), 14 (US male), 15.5 (US female) or 48 (EU sizing).^[64]

Dimension

In measurement, the term "linear foot" (sometimes incorrectly referred to as "lineal foot") refers to the number of feet in a length of material (such as lumber or fabric) without regard to the width; it is used to distinguish from surface area in square foot.^[65]

See also

• Anthropic units
• History of measurement
• International System of Units
• Korean units of measurement
• Mermin's foot
• Pous
• Systems of measurement

Notes

1. Book: BS350:Part 1:1974 Conversion factors and tables Part 1. Basis of tables. Conversion factors . 1974 . British Standards Institution . 5, 91.
2. Book: Chicago Manual of Style . 17th . 2017 . University of Chicago Press . ¶ 10.66.
3. Book: https://www.cia.gov/library/publications/the-world-factbook/appendix/appendix-g.html . The World Factbook . January 17, 2007 . . Appendix G – Weights and Measures . February 4, 2007 . live . http://archive.wikiwix.com/cache/20110223164402/https://www.cia.gov/library/publications/the-world-factbook/appendix/appendix-g.html . February 23, 2011 .
4. News: Will British people ever think in metric?. BBC. December 21, 2011. Jon. Kelly. live. https://web.archive.org/web/20120424232814/http://www.bbc.co.uk/news/magazine-16245391. April 24, 2012.
5. Alder, Ken (2002). The Measure of all Things—The Seven-Year-Odyssey that Transformed the World. London: Abacus.
6. Weights and Measures Act, accessed January 2012, Act current to January 18, 2012. Basis for units of measurement 4.(1) All units of measurement used in Canada shall be determined on the basis of the International System of Units established by the General Conference of Weights and Measures. (...) 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).
7. Encyclopedia: foot, noun . Oxford English Dictionary . Oxford University Press . June 13, 2024 .
8. Book: Oswald Ashton Wentworth Dilke. Oswald A.W. Dilke. Mathematics and measurement. February 2, 2012. May 22, 1987. University of California Press. 978-0-520-06072-2. 23.
9. Sexual dimorphism in foot length proportionate to stature . Daniel M . Fessler . Kevin J . Haley . Roshni D . Lal . Annals of Human Biology . January–February 2005 . 32 . 1 . 44–59 . 10.1080/03014460400027581 . 15788354 . 194735 . dead . https://web.archive.org/web/20110608084140/http://www.sscnet.ucla.edu/anthro/faculty/fessler/pubs/AHBFootSizeDimorphism.pdf . June 8, 2011. mdy-all.
10. Kenoyer JM (2010) "Measuring the Harappan world," in Morley I & Renfrew C (edd) The Archaeology of Measurement, 117; Web site: Archived copy . January 11, 2015 . dead . https://web.archive.org/web/20150626134828/http://a.harappa.com/sites/g/files/g65461/f/Kenoyer%202010%20Measuring%20the%20Harappan%20World.pdf . June 26, 2015 .
11. Web site: History of Herodotus : a new English version. Herodotus. George. Rawlinson. May 14, 1861. New York D. Appleton. Internet Archive.
12. Web site: Epidauros, Stadium (Building). www.perseus.tufts.edu. live. https://web.archive.org/web/20170510073158/http://www.perseus.tufts.edu/hopper/artifact?name=Epidauros%2C+Stadium&object=Building. May 10, 2017.
13. Hosch, William L. (ed.) (2010) The Britannica Guide to Numbers and Measurement New York, NY: Britannica Educational Publications, 1st edition., p.206
14. Book: Oswald Ashton Wentworth Dilke. Oswald A.W. Dilke. Mathematics and measurement. February 2, 2012. May 22, 1987. University of California Press. 978-0-520-06072-2. 26.
15. Duncan-Jones . R. P. . 1980 . Length-Units in Roman Town Planning: The Pes Monetalis and the Pes Drusianus . Britannia . 11 . 127–133 . 10.2307/525675. 525675 . 164149478 .
16. Web site: How Many? A Dictionary of Units of Measurement . Russ Rowlett . . February 28, 2011. live . https://web.archive.org/web/20121224005450/http://www.unc.edu/~rowlett/units/dictT.html . December 24, 2012. mdy-all.
17. The original reference was given in a round number of centimeters.
18. 987740. Elizabeth R. Sutherland. Journal of the Society of Architectural Historians. Feet and dates at Charlieu. May 1957. 16. 2. 2–5. 10.2307/987740.
19. Book: Geometrei. Von künstlichem Feldmessen und absehen . 1535 . Jacob Koebel . de . live . https://web.archive.org/web/20111116021207/http://www.robweir.com/blog/2007/12/right-and-lawful-rood.html . November 16, 2011. mdy-all . Jacob Koebel.
20. Web site: Geometrey . digital.slub-dresden.de . Saxon State Library . February 22, 2019 . de-DE.
21. Teather . Anne . etal. Getting the Measure of Stonehenge . . February 8, 2019 . 165 . 48–51.
22. Book: Great Britain. The statutes at large: from the Magna Charta, to the end of the eleventh Parliament of Great Britain, anno 1761 (continued to 1807). November 30, 2011. 1. 1762. Printed by J. Bentham. 400.
23. Book: Zupko, Ronald Edward . Ronald Edward Zupko . British Weights and Measures: A History from Antiquity to the Seventeenth Century . University of Wisconsin Press . 1977 . 978-0-299-07340-4 . 6, 10, 20 .
24. Web site: 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? . . July 24, 2012. dead . https://web.archive.org/web/20120807195334/http://www.npl.co.uk/reference/faqs/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-(faq-length) . August 7, 2012. mdy-all.
25. Web site: Recommended Unit Symbols, SI Prefixes, and Abbreviations. April 7, 2021.
26. Book: Chicago Manual of Style . 17th . 2017 . University of Chicago Press . ¶ 10.66.
27. See, for example, Report on the Comparisons of the Parliamentary Copies of the Imperial Standards with the Imperial Standard Yard and the Imperial Standard Pound and with each other during the Years 1947 to 1948 (H.M.S.O., London, 1950). Report on the Comparisons of the Parliamentary Copies of the Imperial Standards with each other during the Year 1957 (H.M.S.O., London, 1958).
28. Bigg, P. H. . Anderton, Pamela . March 1964 . The United Kingdom standards of the yard in terms of the meter . dead . British Journal of Applied Physics . 15 . 3 . 291–300 . 10.1088/0508-3443/15/3/308 . 1964BJAP...15..291B . https://archive.today/20120803014104/http://iopscience.iop.org/0508-3443/15/3/308 . August 3, 2012 . May 16, 2009 .
29. http://www.bailii.org/ew/cases/EWHC/Admin/2002/195.html Thoburn v Sunderland City Council [2002] EWHC 195 (Admin) (18 February 2002)
30. 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 June 30, 1959)
31. Web site: U.S. Survey Foot. National Institute of Standards and Technology. 2024-04-04. 2023-01-04.
32. https://www.ngs.noaa.gov/web/news/measure-unit-change-coming.shtml "Measuring Unit Change Coming in 2022"
33. News: Mitchell. Alanna. August 18, 2020. America Has Two Feet. It's About to Lose One of Them. en-US. The New York Times. August 19, 2020. 0362-4331.
34. Web site: Deprecation of the United States (U.S.) Survey Foot . Federal Register . October 5, 2020.
35. https://www.ngs.noaa.gov/SPCS/maps.shtml#spcs83 "State Plane Coordinate System"
36. Schedule to the Standards of Weights and Measures Act, 1976.
37. [Survey of India]
38. Web site: Un historique du mètre . fr . Denis Février . Ministère de l'Économie, des Finances et de l'Industrie . March 10, 2011. live . https://web.archive.org/web/20110228185545/http://www.industrie.gouv.fr/metro/aquoisert/metre.htm . February 28, 2011. mdy-all.
39. Web site: Amtliche Maßeinheiten in Europa 1842 . de . Official measures in Europe 1842 . September 22, 2012. live . https://web.archive.org/web/20130723074500/http://www.spasslernen.de/geschichte/groessen/mas4.htm . July 23, 2013. mdy-all.
40. Book: d'Anville , Jean Baptiste Bourguignon . Traité des mesures itinéraires anciennes et modernes. fr. Treatise of ancient and modern measures of distance. 1769. Paris. de l'Imprimerie Royale. October 24, 2011 .
41. Book: Palaiseau , JFG . Métrologie universelle, ancienne et moderne: ou rapport des poids et mesures des empires, royaumes, duchés et principautés des quatre parties du monde. Bordeaux. October 1816. October 30, 2011.
42. Book: Allereerste Gronden der Cijferkunst. Jacob de Gelder. 's-Gravenhage (The Hague) and Amsterdam. nl. 1824. 163–176. de Gebroeders van Cleef. Introduction to Numeracy. March 2, 2011.
43. Book: Doursther , Horace . Dictionnaire universel des poids et mesures anciens et modernes. Brussels. M. Hayez. October 25, 2011. 1840. liege.. 402–418.
44. Book: Vollständiges tasehenbuch der Münz-, Maass- und Gewichts-Verhältnisse etc. aller Länder und Handelsplätze. de. Comprehensive pocketbook of money, weights and measures for all counties and trading centres. Christian. Noback. Friedrich Eduard. Noback. 1851. I. Leipzig. F. А. Brockhaus. October 24, 2011.
45. Book: Vollständiges tasehenbuch der Münz-, Maass- und Gewichts-Verhältnisse etc. aller Länder und Handelsplätze. de. Comprehensive pocketbook of money, weights and measures for all counties and trading centres. Christian. Noback. Friedrich Eduard. Noback. 1851. II. Leipzig. F. А. Brockhaus. October 24, 2011.
46. Book: Bruhns , Carl . new manual of logarithms to seven places of decimals. 610. Bernhard Tauchnitz. Leipzig. 1881. October 26, 2011.
47. Web site: Plan for Establishing Uniformity in the Coinage, Weights, and Measures of the United States . Thomas Jefferson . July 13, 1790. November 8, 2011 . . live . http://archive.wikiwix.com/cache/20110606150632/http://avalon.law.yale.edu/18th_century/jeffplan.asp . June 6, 2011. Thomas Jefferson.
48. Book: de Gelder , Jacob . Allereerste Gronden der Cijferkunst. The Hague and Amsterdam. nl. 1824. 155–157. De Gebroeders van Cleef. Introduction to Numeracy. March 2, 2011.
49. Web site: Metrologie . de . Andreas . Dreizler . April 20, 2009 . Technical University of Darmstadt . March 28, 2011 . etal .
50. [:File:Fußmaße1.jpg|File]
51. Web site: Maten en gewichten. nl. Weights and measures. Vlaamse Vereniging voor Familiekunde (Flemish Association for Family History). October 24, 2011. 2011. dead. https://web.archive.org/web/20120425091424/http://www.familiekunde-vlaanderen.be/maten-en-gewichten. April 25, 2012.
52. Web site: Les anciennes unités et leurs équivalences . Old units and their equivalences . fr . Le Cybergroupe Généalogique de Charente Poitevine . 2011 . February 25, 2011. live . https://web.archive.org/web/20110720204605/http://www.cgcp.asso.fr/FAQ/divers/anciennes_unites.php . July 20, 2011. mdy-all.
53. The original meter was computed using pre-metric French units.
54. Bibliothèque de l'École des chartes. De l'équivalence des anciennes mesures. A propos d'une publication récente. Values of ancient measures quoted in recent publications. fr. 1913. 74. 267–328. P. Guilhiermoz. 10.3406/bec.1913.448498.
55. Book: Rose , Joshua . Pattern Makers Assistant . D. van Nostrand Co. . 9th . 1900 . New York . 264 .
56. News: Mål, vekt og norsk selvstendighet. no. Dimensions, weight and Norwegian independence. Aftenposten. July 21, 2005. leif. halbo.
57. The Norwegian Norwegian: fot was defined in 1824 as the length of a (theoretical) pendulum that would have a period of  seconds at 45° from the equator.
58. – Information copied from
59. Prior to 1835, the Portuguese: pé or foot was not used in Portugal; instead a palm was used. In 1835 the size of the palm was increased from 217.37 mm (according to Palaiseau) to 220 mm.
60. Web site: The Cape Geodetic Standards and Their Impact on Africa . Tomasz Zakiewicz . FIG . Cairo . April 2005 . January 4, 2012. live . https://web.archive.org/web/20120120235610/http://www.fig.net/pub/cairo/papers/wshs_03/wshs03_02_zakiewich.pdf . January 20, 2012. mdy-all.
61. The source document used pre-metric French units (French: pied, French: pouce and French: ligne).
62. Web site: Scottish Weights and Measures: Distance and Area . Scottish Archive Network . January 28, 2010. live . https://web.archive.org/web/20090814193601/http://www.scan.org.uk/measures/distance.asp . August 14, 2009. mdy-all.
63. The Scots foot ceased to be legal after the Act of Union in 1707.
64. Web site: Why are shoe sizes as they are? . Melissa . Today I found out . 30 March 2016. (12×3=36. US(m): 36−22=14, UK: 36−23=13, EU:30.5×1.5=45.75 then +2 "for comfort" plus rounding = 48)
65. Web site: Units: L . September 20, 2021 . July 2, 2016 . https://web.archive.org/web/20160702030033/http://www.unc.edu/~rowlett/units/dictL.html . dead .