A yard is a unit
Units of measurement
A unit of measurement is a definite magnitude of a physical quantity, defined and adopted by convention and/or by law, that is used as a standard for measurement of the same physical quantity. Any other value of the physical quantity can be expressed as a simple multiple of the unit of...

 of length
In geometric measurements, length most commonly refers to the longest dimension of an object.In certain contexts, the term "length" is reserved for a certain dimension of an object along which the length is measured. For example it is possible to cut a length of a wire which is shorter than wire...

 in several different systems including English unit
English unit
English units are the historical units of measurement used in England up to 1824, which evolved as a combination of the Anglo-Saxon and Roman systems of units...

s, Imperial unit
Imperial unit
The system of imperial units or the imperial system is the system of units first defined in the British Weights and Measures Act of 1824, which was later refined and reduced. The system came into official use across the British Empire...

s and United States customary units
United States customary units
United States customary units are a system of measurements commonly used in the United States. Many U.S. units are virtually identical to their imperial counterparts, but the U.S. customary system developed from English units used in the British Empire before the system of imperial units was...

. It is equal to 3 feet or 36 inch
An inch is the name of a unit of length in a number of different systems, including Imperial units, and United States customary units. There are 36 inches in a yard and 12 inches in a foot...

es. Under an agreement in 1959 between Australia, Canada, New Zealand, South Africa, the United Kingdom and the United States, the yard (known as the "international yard" in the United States) was legally defined to be exactly 0.9144 metre
The metre , symbol m, is the base unit of length in the International System of Units . Originally intended to be one ten-millionth of the distance from the Earth's equator to the North Pole , its definition has been periodically refined to reflect growing knowledge of metrology...

s. Prior to that date, the legal definition of the yard when expressed in terms of metric units varied slightly from country to country.

Equivalence to other units of length

1 international yard is equal to:
  • 3 feet
  • 36 inch
    An inch is the name of a unit of length in a number of different systems, including Imperial units, and United States customary units. There are 36 inches in a yard and 12 inches in a foot...

  • 0.9144 metres (1 metre is equal to about 1.0936 international yards)

The early yard was divided by the binary method into two, four, eight and sixteen parts called the half-yard, span (unit)
Span (unit)
A span is the distance measured by a human hand, from the tip of the thumb to the tip of the little finger. In ancient times, a span was considered to be half a cubit...

, finger (unit)
Finger (unit)
A finger , is usually seven eighths of an inch or 2.2225 cm . The width of an adult human male finger tip is indeed about two centimetres. The inch, on the other hand, originates in the breadth of a thumb. In English this unit has mostly fallen out of use....

 and nail (unit)
Nail (unit)
A nail, when used as a unit, is usually one sixteenth of a certain base unit. In English usage the most common base units were the foot and the yard for length, the acre for area and the hundredweight for mass....

 respectively. Two yards are a fathom
A fathom is a unit of length in the imperial and the U.S. customary systems, used especially for measuring the depth of water.There are 2 yards in an imperial or U.S. fathom...


Historical origin

The yard derives its name from the word for a straight branch or rod, although the precise origin of the measure is not definitely known. Some believe it derived from the double cubit
The cubit is a traditional unit of length, based on the length of the forearm. Cubits of various lengths were employed in many parts of the world in Antiquity, in the Middle Ages and into Early Modern Times....

, or that it originated from cubic measure, others from its near equivalents, like the length of a stride or pace. One postulate was that the yard was derived from the girth
In graph theory, the girth of a graph is the length of a shortest cycle contained in the graph. If the graph does not contain any cycles , its girth is defined to be infinity....

 of a person's waist, while another claim held that the measure was invented by Henry I of England
Henry I of England
Henry I was the fourth son of William I of England. He succeeded his elder brother William II as King of England in 1100 and defeated his eldest brother, Robert Curthose, to become Duke of Normandy in 1106...

 as being the distance between the tip of his nose and the end of his thumb.

It was first defined in law by Edward I of England
Edward I of England
Edward I , also known as Edward Longshanks and the Hammer of the Scots, was King of England from 1272 to 1307. The first son of Henry III, Edward was involved early in the political intrigues of his father's reign, which included an outright rebellion by the English barons...

 in 1305, and again by Edward III of England
Edward III of England
Edward III was King of England from 1327 until his death and is noted for his military success. Restoring royal authority after the disastrous reign of his father, Edward II, Edward III went on to transform the Kingdom of England into one of the most formidable military powers in Europe...

 in 1353. Edward I's law stated "It is ordained that three grains of barley, dry and round, make an inch
An inch is the name of a unit of length in a number of different systems, including Imperial units, and United States customary units. There are 36 inches in a yard and 12 inches in a foot...

; 12 inches make a foot; 3 feet make an "ulna"; 5½ ulne make a perch; and 40 perches in length and 4 perches in breadth make an acre
". It goes on to make reference to "the Iron Ulna of our Lord the King [that] contains 3 feet and no more".

Watson is of the opinion that the purpose of Edward I's legislation was to unify the measures of land and shorter units of length into a single system of measure, and that the words "3 feet and no more" were added to ensure the perch and chain were the same throughout the kingdom; the "iron ulna of ... the King" being nothing more that the mechanism by which this unification was achieved. He dismisses as "childish" the suggestion that the original yard was the length of the king's arm.

In the mid-18th century Graham compared the standard yard of the Royal Society to other existing standards. These were a "long-disused" standard made in the time of Henry VIII
Henry VIII of England
Henry VIII was King of England from 21 April 1509 until his death. He was Lord, and later King, of Ireland, as well as continuing the nominal claim by the English monarchs to the Kingdom of France...

, and a brass yard and a brass ell
An ell , is a unit of measurement, approximating the length of a man's arm.Several national forms existed, with different lengths, includingthe Scottish ell ,the Flemish ell ,the French ell...

 from the time of Queen Elizabeth
Elizabeth I of England
Elizabeth I was queen regnant of England and Ireland from 17 November 1558 until her death. Sometimes called The Virgin Queen, Gloriana, or Good Queen Bess, Elizabeth was the fifth and last monarch of the Tudor dynasty...

 and still in current use, held at the Exchequer; a brass yard and a brass ell at the Guildhall
A guildhall, or guild hall, is a building historically used by guilds for meetings and other purposes. It is also the official or colloquial name for many of these specific buildings, now often used as town halls or museums....

; and a brass yard presented to the Clock-Makers' Company by the Exchequer in 1671. The Exchequer yard was taken as "true"; the variation was found to be + to - of an inch, and an additional graduation for the Exchequer yard was made on the Royal Society's standard. In 1758 the legislature required the construction of a standard yard, which was made from the Royal Society's standard and was deposited with the clerk of the House of Commons
House of Commons of England
The House of Commons of England was the lower house of the Parliament of England from its development in the 14th century to the union of England and Scotland in 1707, when it was replaced by the House of Commons of Great Britain...

; it was divided into feet, one of the feet into inches, and one of the inches into tenths. A copy of it, but with upright cheeks between which other measuring rods could be placed, was made for the Exchequer for commercial use.

Following Royal Society
Royal Society
The Royal Society of London for Improving Natural Knowledge, known simply as the Royal Society, is a learned society for science, and is possibly the oldest such society in existence. Founded in November 1660, it was granted a Royal Charter by King Charles II as the "Royal Society of London"...

 investigations by John Playfair
John Playfair
John Playfair FRSE, FRS was a Scottish scientist and mathematician, and a professor of natural philosophy at the University of Edinburgh. He is perhaps best known for his book Illustrations of the Huttonian Theory of the Earth , which summarized the work of James Hutton...

, Hyde Wollaston
William Hyde Wollaston
William Hyde Wollaston FRS was an English chemist and physicist who is famous for discovering two chemical elements and for developing a way to process platinum ore.-Biography:...

 and John Warner in 1814 a committee of parliament proposed defining the standard yard based upon the length of a seconds pendulum
Seconds pendulum
A seconds pendulum is a pendulum whose period is precisely two seconds; one second for a swing in one direction and one second for the return swing, a frequency of 1/2 Hz....

. This was enacted in 1824. This is 39.1392 inches, and can be derived from the number of beats (86,400) between two meridians
Meridian (geography)
A meridian is an imaginary line on the Earth's surface from the North Pole to the South Pole that connects all locations along it with a given longitude. The position of a point along the meridian is given by its latitude. Each meridian is perpendicular to all circles of latitude...

 of the sun. The temperature compensated pendulum was to be held in a vacuum at sea level in Greenwich, London to give the length of the standard yard. However, a new physical Imperial Standard Yard was authorised by the Weights and Measures Act 1878, and was the legal standard in the United Kingdom until 1964. The "United Kingdom primary standard of the yard" (the old "Imperial Standard Yard") was measured as  meters in May 1963, one part in 300,000 shorter than the international yard that became the new legal standard, and was found to be shortening at a rate of about one part per million every 23 years.

Current use

The yard is used as the standard unit of field-length measurement in American
American football
American football is a sport played between two teams of eleven with the objective of scoring points by advancing the ball into the opposing team's end zone. Known in the United States simply as football, it may also be referred to informally as gridiron football. The ball can be advanced by...

, Canadian
Canadian football
Canadian football is a form of gridiron football played exclusively in Canada in which two teams of 12 players each compete for territorial control of a field of play long and wide attempting to advance a pointed prolate spheroid ball into the opposing team's scoring area...

 and Association football, in addition to Cricket
Cricket pitch
In the game of cricket, the cricket pitch consists of the central strip of the cricket field between the wickets - 1 chain or 22 yards long and 10 feet wide. The surface is very flat and normally covered with extremely short grass though this grass is soon removed by wear at the ends of the...

 and Golf
Golf is a precision club and ball sport, in which competing players use many types of clubs to hit balls into a series of holes on a golf course using the fewest number of strokes....

 hole measurement for some countries.

There are corresponding units of area
Area is a quantity that expresses the extent of a two-dimensional surface or shape in the plane. Area can be understood as the amount of material with a given thickness that would be necessary to fashion a model of the shape, or the amount of paint necessary to cover the surface with a single coat...

 and volume
Volume is the quantity of three-dimensional space enclosed by some closed boundary, for example, the space that a substance or shape occupies or contains....

: the square yard
Square yard
The square yard is an imperial/US customary unit of area, formerly used in most of the English-speaking world but now generally replaced by the square metre outside of the U.S., Canada and the U.K. It is defined as the area of a square with sides of one yard in length...

 and cubic yard
Cubic yard
A cubic yard is an Imperial / U.S. customary unit of volume, used in the United States, Canada, and the UK. It is defined as the volume of a cube with sides of 1 yard in length.-Symbols:...

 respectively. These are sometimes referred to simply as "yards" when no ambiguity is possible, for example an American or Canadian concrete mixer
Concrete mixer
A concrete mixer is a device that homogeneously combines cement, aggregate such as sand or gravel, and water to form concrete. A typical concrete mixer uses a revolving drum to mix the components...

 may be marked with a capacity of "11 yards" or "1.5 yards", where cubic yards are obviously referred to.

Yards are also used in road signs on roads in the United Kingdom and the United States to specify short distances.

See also

  • Anthropic units
    Anthropic units
    Anthropic units are units of measurement which explicitly arose from human physiology or behavior. Some were derived directly from the dimensions of the human body, and as such, are commonly referred to as anthropomorphic...

  • English units
  • Guz
    A guz , also written as gaz, guzz, guj or gudge, is an obsolete unit of length used in parts of Asia. It is a regionally variable measurement, corresponding culturally to the yard in that it was often used for measuring textiles...

    , the yard of the Middle East
    Middle East
    The Middle East is a region that encompasses Western Asia and Northern Africa. It is often used as a synonym for Near East, in opposition to Far East...

  • Imperial units
  • United States customary units
    United States customary units
    United States customary units are a system of measurements commonly used in the United States. Many U.S. units are virtually identical to their imperial counterparts, but the U.S. customary system developed from English units used in the British Empire before the system of imperial units was...

  • Vara
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