An acre is the area of a rectangle, whose length is one furlong and width one chain.
Acre is an English unit of area, which is also used in the United States and some Commonwealth countries. It is most often used to describe areas of land.
An acre is approximately equal:
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.