Acre
From Free net encyclopedia
An acre is an English unit of area, which is also frequently used in the United States and some Commonwealth countries. It is most often used to describe areas of land.
Contents |
UK definition
The acre in the UK is 43,560 square feet or 4,840 square yards. The The Units of Measurement Regulations 1995 express the conversion factor of 4,046.8564224 m², based on the definition of the yard in the Weights and Measures Act of 1963.
U.S. customary units
The U.S. customary units definition of the acre in NIST Handbook 44 is 43,560 square feet. However, the U.S. has two slightly different definitions of foot (international and survey) and thus two definitions of acre:
- The international acre is 4,046.8564224 m². This is based on a foot of 0.3048 m.
- The U.S. survey acre is about 4,046.87261 m². This is based on a foot of Template:Frac0 m.
Although these being used interchangably in most contexts due to the popular unawareness of a special survey defintion, the survey acre is actually the standard one.
Related measurements
Two obsolete, but related, linear measurements are the acre’s length and the acre’s breadth.
- 1 acre’s length = 1 furlong = 40 poles = 220 yards = Template:Frac0 mile
- 1 acre’s breadth = 1 chain = 4 poles = 22 yards = Template:Frac0 furlong
Conversion
An international acre may be converted to other units because it is equivalent to exactly:
- 4,046.8564224 m² (SI unit) = 40.468564224 a = 0.40468564224 ha,
- 43,560 square feet,
- 4,840 square yards,
- 160 square rods,
- 4 rood,
- 1/640 square mile,
- 1 furlong × 1 chain (a 10:1 rectangle),
- 10 square chains,
- 100 cents (India).
An acre is equivalent to approximately:
- a square of side 208.71 feet (63.61 m).
One square mile is 640 acres. A square parcel of land ¼ mile wide is 40 acres. A square parcel of land ½ mile on a side (i.e. a quarter-section) is 160 acres, the usual land tract under the Homestead Act in the United States. This results in common field lengths of ½ mile, with every rod in width equal to one acre.
One acre is slightly less than 91 yards on an American Football field, with the full field, including the end zones, covering approximately 1.32 acres.
History
The acre was selected as approximately the amount of land tillable by one man behind an ox in one day; its name comes from ager, the Latin for “field”. This explains its rectangular definition as a one-chain by one-furlong (66 foot × 660 foot) parcel of land: 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. In fact, the name for the related unit, the “furlong”, comes 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.
In the UK the use of acres is now officially discouraged, but it remains a very familiar measure of land with the general public, especially among middle-aged and elderly people.
An acre is a measure of “flat” area, not actual area. To understand this, visualize a rectangle one furlong long by one chain wide drawn on a map. The area enclosed by this rectangle is defined to be an acre—and on perfectly level ground the actual area will be one acre. On sloping ground, however, the actual area of the terrain, as calculated mathematically, will be greater than an acre.
Spanish Landgrant System
In the archaic system of old Spanish land grants affecting Texas and parts of adjoining states, two other measures of land are used, the (square) league and the labor. (Labor is pronounced "Luh-BOR" in West Texas).
The league is equivalent to 4,428 acres and the Labor to 177 acres. The labor is often used as an approximate equivalent to a quarter-section, i.e. one-quarter of a square mile, of land. These measures are still encountered in modern real estate transcations.
See also
External links
da:Acre (arealenhed) de:Acre (Einheit) eo:Akreo (mezurunuo) fr:Acre (unité) he:אקר nl:Acre (oppervlaktemaat) ja:エーカー no:Acre (måleenhet) pl:Akr pt:Acre (unidade) ru:Акр simple:Acre sl:Aker ta:ஏக்கர் vi:Mẫu Anh uk:Акр zh:英亩