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:''This entry is about the unit of area. For other meanings see Acre (disambiguation)''
An 'acre' is the name of a unit of area in a number of different systems, including Imperial units and United States customary units. The most commonly used acres today are the international acre and, in the United States, the survey acre.

One acre comprises 4,840 square yards or 43,560 square feet. Because of alternative definitions of a yard or a foot, the exact size of an acre also varies slightly. Traditionally, an acre was a swath of land one furlong long and one chain wide. A modern acre can have arbitrary dimensions as long as the area is correct. For example, a strip of land 1 inch wide and 99 miles long is also an acre.
The acre is often used to express areas of land. In the metric system, the hectare is commonly used for the same purpose. An acre is approximately 0.4 hectare.
One acre is 90.75 yards of a 53.33-yard-wide American football field. The full field, including the end zones, covers approximately 1.32 acres.

Contents

International acre

United States survey acre

Equivalence to other units of area

Historical origin

Other acres

References

See also

External links

International acre

In 1958, the United States and countries of the Commonwealth of Nations defined the length of the international yard to be 0.9144 meters.^[1] Consequently, the international acre is exactly 4046.8564224 square meters.

United States survey acre

The United States survey acre is approximately 4046.873 square meters; its exact value ( m²) is based on an inch defined by 1 meter = 39.37 inches exactly, as established by the Mendenhall Order. It is the standard acre in the United States, but the fractional difference from the international acre is only 4 millionths, or 4 ten-thousandths of one percent.

Equivalence to other units of area

1 international acre is equal to the following metric units:

★ 4046.8564224 square meters

★ 0.40468564224 hectare
1 United States survey acre is equal to:

★ 4046.87261 square meters

★ 0.404687261 hectare
1 acre (both variants) is equal to the following customary units:

★ 66 feet × 660 feet (43,560 square feet)

★ 4840 square yards

★ 160 perches. A Perch is equal to a square rod (1 square rod is 0.00625 acre)

★ 10 square chains

★ 4 roods

★ A chain by a furlong (chain 22 yards, furlong 220 yards)

★ 0.0015625 square mile (1 square mile is equal to 640 acres)
1 international acre is equal to the following Indian unit:

★ 100 Indian cents (1 cent is equal to 0.01 acre)

Historical origin

The word "acre" is derived from Old English ''æcer'' (originally meaning "open field", cognate to German ''Acker'', Latin ''ager'' and Greek ''agros'').
The acre was selected as approximately the amount of land tillable by one man behind an ox in one day. This explains one definition as the area of a rectangle with sides of length one chain and one furlong. A long narrow strip of land is more efficient to plough than a square plot, since the plough does not have to be turned so often. The word "furlong" itself derives from the fact that it is ''one furrow long''.
Statutory values for the acre were enacted in England by acts of:

★ Edward I,

★ Edward III,

★ Henry VIII,

★ George IV and

★ Victoria – the British "Weights and Measures Act" of 1878 defined it as containing 4,840 square yards.
Historically the size of farms and landed estates in the United Kingdom was always expressed in acres, even if the number of acres was so large that it might conveniently have been expressed in square miles. For example a certain landowner might have been said to own 32,000 acres of land, not 50 square miles of land.

Other acres

★ 'Scottish acre', one of a number of obsolete Scottish units of measurement

References

1. National Bureau of Standards. Refinement of Values for the Yard and the Pound.

See also

★ Conversion of units

★ Acre-foot

★ Obsolete Spanish and Portuguese units of measurement

External links

★ The Units of Measurement Regulations 1995

★ Acre Conversion

★ Cockeyed.com presents "How much is inside an acre?"