acre definition
The acre is a unit of land area used in the imperial and US customary systems. It is defined as the area of 1 chain (22 yards) by 1 furlong (220 yards), which is exactly equal to 1â640 of a square mile, approximately 4,046.856 m 2, or about 40% of a hectare.ince the difference between the US survey acre and international acre is only about a quarter of the size of an A4 sheet of paper (0.016 square metres, 160 square centimetres or 24.8 square inches), it is usually not important which one is being discussed.