ABCDEFGHIJKLMNOPQRSTUVWXYZ Definition of Acre more ... A US Standard Unit of area, usually used to measure land. 1 acre = 4,840 square yards. 1 acre is about 0.4 hectares in the Metric system, or exactly 4,046.8564224 square meters. ../geometry/images/area-user.js?mode=acre See: Hectare (ha), Square Meter, Area US Standard Area