Acre

: This article is about the unit of measure known as the acre. For other definitions, see Acre (disambiguation).

An acre is an English unit of area. It is most frequently used to describe areas of land.

UK definition

The UK has a definition of the acre in The Units of Measurement Regulations 1995 as 4 046.856 422 4 m². This is equivalent to 43 560 square feet using the definition of foot in the same source.

US definition

The US has a definition of the acre in NIST Handbook 44 as 43 560 square feet. However, the US has two definitions of foot (international foot and survey foot) and thus two definitions of acre:

The international acre is 4 046.856 422 4 m². This is based on international foot of 0.3048 m.
The US survey acre is 4 046.872 61 m². This is based on the US 'survey foot'' of 1200/3937 m.

Related linear measurements

Two obsolete, but related, measurements are the acre's length and the acre's breadth.

1 acre's length = 1 Furlong, 40 poles, or 220 yards
1 acre's breadth = 1 chain, 4 poles, or 22 yards

Conversion

An international acre is equivalent to exactly:

4 046.856 422 4 m² (SI unit)
40.468 564 224 a,
0.404 685 642 24 ha,
43 560 square feet,
4840 square yards,
160 square rods,
4 Rood,
1/640 square mile,
a 10:1 rectangle of 1 Furlong by 1 chain.

An acre is equivalent to approximately:

a square of side 208.71 feet (63.61 metres).

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 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.

An American Football field covers 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. This explains its rectangular definition one-chain by one-Furlong 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. Statutory values were enacted in England by acts of