- For the state in Brazil, see Acre (state).
- By the official definition it is 4,046.8564224 m2 (4,840 square yards). It is the area of one furlong by one chain.
- The international acre is 4,046.8564224 m2, or 0.404686 hectares. This is based on international foot of 0.3048 m.
An acre is approximately equal:
- the area of an American football field.
Originally, it was seen as the area of land a farmer could plough with an ox in a day. Since this definition depended on the farmer and the ox, it looked variable. Therefore, Edward I, Edward III, Henry VIII and George IV passed laws fixing its size. The Commonwealth countries, including the United States then also introduced these laws.