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The foot ( feet), standard symbol: ft, is a unit 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 Inte ...
in the British imperial and United States customary systems of
measurement Measurement is the quantification of attributes of an object or event, which can be used to compare with other objects or events. In other words, measurement is a process of determining how large or small a physical quantity is as compared ...
. The prime symbol, , is a customarily used alternative symbol. Since the
International Yard and Pound Agreement 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 ...
of 1959, one foot is defined as 0.3048 
meters The metre (British spelling) or meter (American spelling; see spelling differences) (from the French unit , from the Greek noun , "measure"), symbol m, is the primary unit of length in the International System of Units (SI), though its pr ...
exactly. In both customary and imperial units, one foot comprises 12 
inch Measuring tape with inches The inch (symbol: in or ″) is a unit of length in the British imperial and the United States customary systems of measurement. It is equal to yard or of a foot. Derived from the Roman uncia ("twelfth ...
es and one yard comprises three feet. Historically the "foot" was a part of many local systems of units, including the Greek,
Roman Roman or Romans most often refers to: * Rome, the capital city of Italy * Ancient Rome, Roman civilization from 8th century BC to 5th century AD *Roman people, the people of ancient Rome *''Epistle to the Romans'', shortened to ''Romans'', a lett ...
, Chinese,
French French (french: français(e), link=no) may refer to: * Something of, from, or related to France ** French language, which originated in France, and its various dialects and accents ** French people, a nation and ethnic group identified with Franc ...
, and
English English usually refers to: * English language * English people English may also refer to: Peoples, culture, and language * ''English'', an adjective for something of, from, or related to England ** English national ...
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 nation that uses the international foot and the survey foot (a customary unit of length) in preference to the meter in its commercial, engineering, and standards activities. The foot is legally recognized in the United Kingdom; road signs ''must'' use imperial units (however, distances on road signs are always marked in miles or yards, not feet), while its usage is widespread among the British public as a measurement of height. The foot is recognized as an alternative expression of length in Canada officially defined as a unit derived from the meter although both the U.K. and Canada have partially metricated their units of measurement. The measurement of
altitude Altitude or height (also sometimes known as depth) is a distance measurement, usually in the vertical or "up" direction, between a reference datum and a point or object. The exact definition and reference datum varies according to the context ...
in international
aviation Aviation includes the activities surrounding mechanical flight and the aircraft industry. ''Aircraft'' includes airplane, fixed-wing and helicopter, rotary-wing types, morphable wings, wing-less lifting bodies, as well as aerostat, lighter- ...
is one of the few areas where the foot is used outside the English-speaking world. The length of the international foot corresponds to a human foot with
shoe size A shoe size is an indication of the fitting size of a shoe for a person. There are a number of different shoe-size systems used worldwide. While all shoe sizes use a number to indicate the length of the shoe, they differ in exactly what they me ...
of 13 (UK), 14 (US male), 15.5 (US female) or 48 (EU sizing).


Historical origin

Historically, the human body has been used to provide the basis for units of length. The foot of an adult Caucasian male is typically about 15.3% of his height, giving a person of a foot-length of about , on average. Archaeologists believe that, in the past, the people of
Egypt Egypt ( ar, مصر , ), officially the Arab Republic of Egypt, is a List of transcontinental countries, transcontinental country spanning the North Africa, northeast corner of Africa and Western Asia, southwest corner of Asia via a land bridg ...
,
India India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area, the List of countries and dependencies by population, second-most populous ...
, and
Mesopotamia Mesopotamia ''Mesopotamíā''; ar, بِلَاد ٱلرَّافِدَيْن or ; syc, ܐܪܡ ܢܗܪ̈ܝܢ, or , ) is a historical region of Western Asia situated within the Tigris–Euphrates river system, in the northern part of the ...
preferred the
cubit The cubit is an ancient unit of length based on the distance from the elbow to the tip of the middle finger. It was primarily associated with the Sumerians, Egyptians, and Israelites. The term ''cubit'' is found in the Bible regarding ...
, while the people of
Rome , established_title = Founded , established_date = 753 BC , founder = King Romulus ( legendary) , image_map = Map of comune of Rome (metropolitan city of Capital Rome, region Lazio, Italy).svg , map_caption ...
,
Greece Greece,, or , romanized: ', officially the Hellenic Republic, is a country in Southeast Europe. It is situated on the southern tip of the Balkans, and is located at the crossroads of Europe, Asia, and Africa. Greece shares land borders wi ...
, and
China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's List of countries and dependencies by population, most populous country, with a Population of China, population exceeding 1.4 billion, slig ...
preferred the foot. Under the Harappan linear measures, Indus cities during the Bronze Age used a foot of 333.5 mm (13.2 in) and a cubit of 528.3 mm (20.8 in). The Egyptian equivalent of the foot—a measure of four palms or 16 digits—was known as the and has been reconstructed as about . The Greek foot (, ) had a length of of a stadion, one stadion being about ; therefore a foot was, at the time, about . Its exact size varied from city to city and could range between and , but lengths used for temple construction appear to have been about to ; the former was close to the size of the Roman foot. The standard
Roman foot Roman or Romans most often refers to: *Rome, the capital city of Italy * Ancient Rome, Roman civilization from 8th century BC to 5th century AD *Roman people, the people of ancient Rome *''Epistle to the Romans'', shortened to ''Romans'', a lette ...
() was normally about (97% of today's measurement),Hosch, William L. (ed.) (2010
''The Britannica Guide to Numbers and Measurement''
New York, NY: Britannica Educational Publications, 1st edition. , p.206
but, in the provinces, the so-called (foot of Nero Claudius Drusus) was used, with a length of about . (In reality, this foot predated Drusus.) 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 (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 Charlemagne ( , ) or Charles the Great ( la, Carolus Magnus; german: Karl der Große; 2 April 747 – 28 January 814), a member of the Carolingian dynasty, was King of the Franks from 768, King of the Lombards from 774, and the first E ...
attempted to reform the units of measure in his domains. His units of length were based on the and in particular the , the distance between the fingertips of the outstretched arms of a man. The has 6 (feet) each of . 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 was used; when it was rebuilt in the 10th century, a foot of about The original reference was given in a round number of centimeters was used. At the same time, monastic buildings used the Carolingian foot of . The procedure for verification of the foot as described in the 16th century posthumously published work by Jacob Köbel in his book is:


England

The
Neolithic The Neolithic period, or New Stone Age, is an Old World archaeological period and the final division of the Stone Age. It saw the Neolithic Revolution, a wide-ranging set of developments that appear to have arisen independently in several pa ...
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 A lintel or lintol is a type of beam (a horizontal structural element) that spans openings such as portals, doors, windows and fireplaces. It can be a decorative architectural element, or a combined ornamented structural item. In the case of ...
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 Yorkshire ( ; abbreviated Yorks), formally known as the County of York, is a Historic counties of England, historic county in northern England and by far the largest in the United Kingdom. Because of its large area in comparison with other Eng ...
(
neolithic The Neolithic period, or New Stone Age, is an Old World archaeological period and the final division of the Stone Age. It saw the Neolithic Revolution, a wide-ranging set of developments that appear to have arisen independently in several pa ...
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. The measures of
Iron Age Britain The British Iron Age is a conventional name used in the archaeology of Great Britain, referring to the prehistoric and protohistoric phases of the Iron Age culture of the main island and the smaller islands, typically excluding prehistoric I ...
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 was introduced to England either by the Belgic Celts during their invasions prior to the Romans or by the
Anglo-Saxons The Anglo-Saxons were a cultural group who inhabited England in the Early Middle Ages. They traced their origins to settlers who came to Britain from mainland Europe in the 5th century. However, the ethnogenesis of the Anglo-Saxons happened ...
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 London is the capital and List of urban areas in the United Kingdom, largest city of England and the United Kingdom, with a population of just under 9 million. It stands on the River Thames in south-east England at the head of a estuary dow ...
.
Henry I Henry I may refer to: 876–1366 * Henry I the Fowler, King of Germany (876–936) * Henry I, Duke of Bavaria (died 955) * Henry I of Austria, Margrave of Austria (died 1018) * Henry I of France (1008–1060) * Henry I the Long, Margrave of the N ...
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 traditionally credited to Edward I or II, the statute foot was a different measure, exactly of the old (Belgic) foot. The barleycorn,
inch Measuring tape with inches The inch (symbol: in or ″) is a unit of length in the British imperial and the United States customary systems of measurement. It is equal to yard or of a foot. Derived from the Roman uncia ("twelfth ...
, ell, and yard were likewise shrunk, while rods and furlongs remained the same. The ambiguity over the state of the
mile The mile, sometimes the international mile or statute mile to distinguish it from other miles, is a British imperial unit and United States customary unit of distance; both are based on the older English unit of length equal to 5,280 Engli ...
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
microscope A microscope () is a laboratory instrument used to examine objects that are too small to be seen by the naked eye. Microscopy is the science of investigating small objects and structures using a microscope. Microscopic means being invisi ...
s, 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 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 C ...
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 U.S. definition and 1.7 ppm longer than the previous British definition. The 1959 agreement concluded a series of step-by-step events, set off in particular by 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 ...
's adoption of a scientific standard inch of 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 in 1930.


Symbol

The IEEE standard symbol for a foot is "ft". In some cases, the foot is denoted 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 ...
, 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 ...
, and the inch by a double prime; for example, 2feet 4 inches is sometimes denoted as 2′4″.


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. 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 , 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.


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 India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area, the List of countries and dependencies by population, second-most populous ...
. 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 The State Plane Coordinate System (SPCS) is a set of 124 geographic zones or coordinate systems designed for specific regions of the United States. Each state contains one or more state plane zones, the boundaries of which usually follow county li ...
(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 __NOTOC__ The retriangulation of Great Britain was a triangulation project carried out between 1935 and 1962 that sought to improve the accuracy of maps made of Great Britain. Data gathered from the retriangulation replaced data gathered during ...
(1936–62) had been done in meters.


U.S. survey foot

In the United States, the foot was defined as 12 inches, with the inch being defined by the Mendenhall Order of 1893 as 39.37 inches = 1 m (making a US foot exactly meters, approximately ). Out of 50 states and six other jurisdictions, 40 have legislated that surveying measures should be based on the U.S. survey foot, six have legislated that they be made on the basis of the international foot, and ten have not specified. 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). The
National Institute of Standards and Technology The National Institute of Standards and Technology (NIST) is an agency of the United States Department of Commerce whose mission is to promote American innovation and industrial competitiveness. NIST's activities are organized into physical s ...
,
National Geodetic Survey The National Geodetic Survey (NGS) is a United States federal agency that defines and manages a national coordinate system, providing the foundation for transportation and communication; mapping and charting; and a large number of applications ...
, and the
United States Department of Commerce The United States Department of Commerce is an executive department of the U.S. federal government concerned with creating the conditions for economic growth and opportunity. Among its tasks are gathering economic and demographic data for bus ...
are phasing out the US survey foot beginning in 2023. However, its relevance may persist, as the Federal Register Notice says: :"The date of December 31, 2022, was selected to accompany the modernization of the National Spatial Reference System (NSRS) by
NOAA The National Oceanic and Atmospheric Administration (abbreviated as NOAA ) is an United States scientific and regulatory agency within the United States Department of Commerce that forecasts weather, monitors oceanic and atmospheric conditio ...
's National Geodetic Survey (NGS). The reason for associating the deprecation of the U.S. survey foot with the modernization of the NSRS is that the biggest impact of the uniform adoption of the international foot will be for users of the NSRS, due to very large coordinate values currently given in U.S. survey feet in many areas of the U.S. Impacts related to the change to international feet will be minimized if a transition occurs concurrently with others changes in the NSRS." :"The difference will have no effect on users of the existing NSRS (National Spatial Reference System), because NGS (
NOAA The National Oceanic and Atmospheric Administration (abbreviated as NOAA ) is an United States scientific and regulatory agency within the United States Department of Commerce that forecasts weather, monitors oceanic and atmospheric conditio ...
's National Geodetic Survey) ''will continue to support the U.S. survey foot for components of the NSRS where it is used now and in the past.'' In other words, to minimize disruption in the use of U.S. survey foot for existing NSRS coordinate systems, the change will apply only to the modernized NSRS."


Indian survey foot

The Indian survey foot is defined as exactly , 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 In the pursuit of knowledge, data (; ) is a collection of discrete values that convey information, describing quantity, quality, fact, statistics, other basic units of meaning, or simply sequences of symbols that may be further interpreted. ...
, which is also used by the
Global Positioning System The Global Positioning System (GPS), originally Navstar GPS, is a satellite-based radionavigation system owned by the United States government and operated by the United States Space Force. It is one of the global navigation satellite ...
.


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 France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of Overseas France, overseas regions and territories in the Americas and the Atlantic Ocean, Atlantic, Pacific Ocean, Pac ...
. This was not fully enforced, and in 1812
Napoleon Napoleon Bonaparte ; it, Napoleone Bonaparte, ; co, Napulione Buonaparte. (born Napoleone Buonaparte; 15 August 1769 – 5 May 1821), later known by his regnal name Napoleon I, was a French military commander and political leader wh ...
introduced the system of ''
mesures usuelles Mesures usuelles (, ''customary measurements'') were a French system of measurement introduced by Napoleon I in 1812 to act as compromise between the metric system and traditional measurements. The system was restricted to use in the retail indu ...
'' 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.


Germany

In southwestern Germany in 1806, the
Confederation of the Rhine The Confederated States of the Rhine, simply known as the Confederation of the Rhine, also known as Napoleonic Germany, was a confederation of German client states established at the behest of Napoleon some months after he defeated Austria a ...
was founded and three different ''reformed feet'' were defined, all of which were based on the metric system: *In
Hesse Hesse (, , ) or Hessia (, ; german: Hessen ), officially the State of Hessen (german: links=no, Land Hessen), is a state in Germany. Its capital city is Wiesbaden, and the largest urban area is Frankfurt. Two other major historic cities are ...
, the ''Fuß'' (foot) was redefined as 25 cm. *In
Baden Baden (; ) is a historical territory in South Germany, in earlier times on both sides of the Upper Rhine but since the Napoleonic Wars only East of the Rhine. History The margraves of Baden originated from the House of Zähringen. Baden i ...
, 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 ''voet'' in
Ypres Ypres ( , ; nl, Ieper ; vls, Yper; german: Ypern ) is a Belgian city and municipality in the province of West Flanders. Though the Dutch name is the official one, the city's French name is most commonly used in English. The municipality ...
, 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 Paris () is the capital and most populous city of France, with an estimated population of 2,165,423 residents in 2019 in an area of more than 105 km² (41 sq mi), making it the 30th most densely populated city in the world in 2020. Si ...
– 1769 *Palaiseau –
Bordeaux Bordeaux ( , ; Gascon oc, Bordèu ; eu, Bordele; it, Bordò; es, Burdeos) is a port city on the river Garonne in the Gironde department, Southwestern France. It is the capital of the Nouvelle-Aquitaine region, as well as the prefectu ...
: 1816 *de Gelder,
Amsterdam Amsterdam ( , , , lit. ''The Dam on the River Amstel'') is the capital and most populous city of the Netherlands, with The Hague being the seat of government. It has a population of 907,976 within the city proper, 1,558,755 in the urban ar ...
and
The Hague The Hague ( ; nl, Den Haag or ) is a city and municipality of the Netherlands, situated on the west coast facing the North Sea. The Hague is the country's administrative centre and its seat of government, and while the official capital o ...
– 1824 *Horace,
Brussels Brussels (french: Bruxelles or ; nl, Brussel ), officially the Brussels-Capital Region (All text and all but one graphic show the English name as Brussels-Capital Region.) (french: link=no, Région de Bruxelles-Capitale; nl, link=no, Bruss ...
– 1840 *Noback & Noback (2 volumes),
Leipzig Leipzig ( , ; Upper Saxon: ) is the most populous city in the German state of Saxony. Leipzig's population of 605,407 inhabitants (1.1 million in the larger urban zone) as of 2021 places the city as Germany's eighth most populous, as ...
– 1851 *Bruhns, Leipzig – 1881 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. 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 ''mesures usuelles'' under Napoleon and the newly formed
German Empire The German Empire (),Herbert Tuttle wrote in September 1881 that the term "Reich" does not literally connote an empire as has been commonly assumed by English-speaking people. The term literally denotes an empire – particularly a hereditary ...
adopted the metric system in 1871. The palm (typically 200 mm to 280 mm) 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 have been chosen. In Belgium, the words ''pied'' (French) and ''voet'' (Dutch) would have been used interchangeably.


Notes


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 level In aviation and aviation meteorology, a flight level (FL) is an aircraft's altitude at standard air pressure, expressed in hundreds of feet. The air pressure is computed assuming an International Standard Atmosphere pressure of 1013.25  ...
s (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).


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 The surface area of a solid object is a measure of the total area that the surface of the object occupies. The mathematical definition of surface area in the presence of curved surfaces is considerably more involved than the definition of ...
in ''
square foot The square foot (plural square feet; abbreviated sq. ft, sf, or ft2; also denoted by '2) is an imperial unit and U.S. customary unit (non- SI, non- metric) of area, used mainly in the United States and partially in Canada, the United Kingdom, B ...
''.


See also

* Anthropic units * History of measurement *
International System of Units The International System of Units, known by the international abbreviation SI in all languages and sometimes pleonastically as the SI system, is the modern form of the metric system and the world's most widely used system of measurement. ...
* Korean units of measurement * Mermin's foot * Pous * Systems of measurement


Notes


References

{{DEFAULTSORT:Foot Customary units of measurement in the United States Human-based units of measurement Imperial units Units of length