How big is one acre of land?

The acre is a unit of land area used in the imperial and US customary systems. It is traditionally defined as the area of one chain by one furlong, which is exactly equal to 10 square chains, ​¹⁄₆₄₀ of a square mile, or 43,560 square feet, and approximately 4,047 m², or about 40% of a hectare.

The word “acre” traces back to the Old English term æcer meaning “open field” and was generally used to describe unoccupied country. In English, it was historically spelled “aker” and was related to the Latin word “ager” meaning “field.” Originally, an acre was the typical area of land that could be plowed by one man, in one day, using a team of oxen and a wooden plow.

It is still a statute measure in the United States. Both the international acre and the US survey acre are in use. The most common use of the acre is to measure tracts of land.

The acre is commonly used in a number of current and former British Commonwealth countries by custom only. In a few it continues as a statute measure, although since 2010 not in the United Kingdom itself, and not since decades ago in Australia, New Zealand and South Africa. In many of those where it is not a statute measure, it is still lawful to "use for trade" if given as supplementary information and is not used for land registration.