- Acre
The

**acre**is a unit ofarea in a number of different systems, including the imperial and U.S. customary systems. The most commonly used acres today are the international acre and, in the United States, the survey acre.One international acre is equal 4046.8564224 m

^{2}. One U.S. survey acre is equal to frac|62,726,400,000|15,499,969 m^{2}= 4046.8726098 m^{2}.One acre comprises 4,840

square yard s or 43,560square feet [*National Institute of Standards and Technology [*] (which can be easily remembered as 44,000 square feet, less 1%). Because of alternative definitions of a yard or a foot, the exact size of an acre also varies slightly. Originally, an acre was a*http://ts.nist.gov/WeightsAndMeasures/Publications/upload/h4402_appenc.pdf General Tables of Units of Measurement*]selion of land onefurlong (660 ft) long and one chain (66 ft) wide. However, an acre is a measure of area, and has no particular width, length or shape.The acre is often used to express areas of land. In the

metric system , thehectare is commonly used for the same purpose. An acre is approximately 40% of a 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.**International acre**In 1958, the

United States and countries of theCommonwealth of Nations defined the length of the internationalyard to be 0.9144meter s. [*National Bureau of Standards. [*] Consequently, the international acre is exactly 4046.8564224*http://geodesy.noaa.gov/PUBS_LIB/FedRegister/FRdoc59-5442.pdf Refinement of Values for the Yard and the Pound*] .square meters .**United States survey acre**The United States survey acre is approximately 4046.873

square meter s; its exact value (frac|4046|13,525,426|15,499,969 m²) is based on an inch defined by 1 meter = 39.37 inches exactly, as established by theMendenhall Order . It is the standard acre in theUnited States , but the fractional difference from the international acre is only 40 millionths, or 4 ten-thousandths of one percent.**Equivalence to other units of area**1 international acre is equal to the following metric units:

* 4046.8564224square meter s

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

* 4046.87261square meter s

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

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

* 1 chain x 10 chains ( 1-chain = 66 feet or 22 yards or 4 rods)

* 1 acre is approximately 208.71 feet x 208.71 feet (square)

* 4840square yard s

* 160 perches. A perch is equal to a square rod (1 square rod is 0.00625 acre)

* 10 square chains

* 4rood s

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

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

* 100India n 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 west coast Norwegian language "ækre" and Swedish "åker", German "Acker",Latin "ager" and Greek "αγρος" ("agros").The acre was approximately the amount of land tillable by one man behind an

ox in oneday . This explains one definition as the area of a rectangle with sides of length one chain and onefurlong . 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 "onefurrow long".Before the enactment of the

metric system , many countries in Europe used their own official acres. These were differently sized in different countries, for instance, the historical French acre was 4221 square metres, whereas inGermany as many variants of "acre" existed as there were German states.Statutory values for the acre were enacted in England by acts of:

* Edward I,

* Edward III,

* Henry VIII,

* George IV and

* Victoria – the BritishWeights 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 usually expressed in acres (or acres,

rood s, and perches), 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.**Customary acre**The customary acre was a measure of roughly similar size to the acre described above, but was subject to considerable local variation. However, there were more ancient measures that were also used, including

carucate s,virgate s,bovate s,nook s, and farundells or farthingales. These may have been multiples of the customary acre, rather than the statute acre.**Other acres***

**Scottish acre**, one of a number ofobsolete Scottish units of measurement

***Irish acre****References****See also***

Anthropic units

*Conversion of units

*Acre-foot

*Obsolete Spanish and Portuguese units of measurement

*Quarter Acre **External links*** [

*http://www.opsi.gov.uk/si/si1995/Uksi_19951804_en_2.htm The Units of Measurement Regulations 1995 (United Kingdom)*]

*Cockeyed.com [*http://cockeyed.com/inside/acre/acre.html presents "How much is inside an acre?"*]

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