Acre (plural Acre / s, English acre, plural acres) is a certificate from the British Isles, centuries-old Anglo-American unit of measurement for area estimation of land. With the current size of roughly 4047 sqm this unit area is similar to the morning or day's work. Is from the Anglo-American Flächenmaßsystem to land and basic surveying today next to the acre - which is the most common unit - practically only the unit area used Square Foot. In the United States, the size of land is given only with these two surface units. Widely used, these units are also in the UK, Canada, India, Australia and other Commonwealth countries, although there today, there is a metric Hauptmaßsystem.

Definition and size

An acre is the area of ​​a surface with the length of one furlong and width 1 chain.

  • Chain ( chain - the length dimension of the width of the field ), and the
  • Furlong ( furrow length - the length dimension for the length of the field).

The chain is based on the length of the " measurement chain " of surveyor.

1 chain = 20.1168 m = 66 ft. The relationship with the square measure Acre is: 1 Chain = 1 acre width. This unit length is come in the USA out of use.

1 Furlong = 10 chain = 201.168 m = 660 ft. The relationship with the square measure Acre is: 1 furlong = 1 acre - length. Also this unit of length in the United States came out of use.

As a result: 1 acre = 1 chain (66 ft) × 1 furlong (660 ft) = 43560 Square Feet or = 1/640 Square Mile. The farmer has his land ie on the aspect ratio of 1: 10 optimized.


Acre is abbreviated ac or ac with a predominant is the abbreviation

Anglo American Maßreform 1959

The world's different Anglo-American units of length 1959 were unified. In the United States, this resulted in an increase by a factor of 1.000002 for the lengths towards the new " international " length measurements used until then. When surveying this would have led to noticeable differences at large distances. With a length of 1000 km, for example, the difference would be 2 m. To the existing values ​​do not need to change was, therefore, in the United States, the old system of units - only for the purpose of land surveying - maintained and the measure of length used previously Foot was designated Survey Foot.

In the United States, the unit area Acre is based on the Survey Foot ( the additional survey is usually omitted ), or the International Foot is the foundation. The based on the U.S. Survey Foot acre is about 162 cm ² slightly larger.

Inclusion in the system of units for land

1 Acre = 10 square chains = 160 Square Rods = 43,560 Square Feet

1 Square Mile = 640 Acres

This classification, however, is only of historical importance, since both the surface unit Square Chain and Square Rod are outdated and no longer used. The corresponding Anglo-American measures of length for the determination of land areas such as Link, Rod, Chain, Furlong nowadays have no meaning and are no longer used.

Practical Uses

The Acre is the main measure for land areas. Usually no more than two decimal places are specified, which have an accuracy of ± 20 m² exists. Once more detailed information is required, such as land, the unit area square foot will be used.

For agricultural land, the surfaces are divided into Workable Acres and Non Workable Acres. By this is meant the actual usable area and the non-usable for agricultural purposes surface, such as wasteland.

Even very large surface areas are given in Acre. For example, 87,000 ac ( ≈ 350 km ²). A conversion into square miles will not usually.

Acre as a basis for derived units

  • In agriculture, the surface yield refers to the acre. For cereals, the yield in bushels / acre is specified. ( See main article bushel ( measure of grain ) )
  • The price of land of all types is given in the United States and Canada in $ / acre.
  • The acre-foot and the acre- inches are units of volume in the United States for large quantities of water, for example in municipal water consumption or for agricultural irrigation.

Historic Scottish units

Before the introduction of the Imperial Standard Acre there was in Scotland one old and one new Scottish Acre:

  • Old Scottish acre, or Ancident Scots acre 1 acre = 5145.55 square meters
  • Compare: 3025 Acre = 3844 Imperial Acre