A farmer could tell you that this measurement of land is equal to 43,560 square feet
It 
is defined as the area of 1 chain by 1 furlong (66 by 660 feet), which is exactly 
equal to 1640 of a square mile, 43,560 square feet, approximately 4,047 m2, ... 
An acre was defined in the Middle Ages, being the amount of land that could be... [DOC] [TLE] Stupid Measurements [PAR] My calculator tells me that an acre is 43,560 square feet (or 4,840 square yards).