One acre is equal to 0.0016 square miles. The value is also equivalent to 4,840 square yards, 43,560 square feet, 0.004047 square kilometers or 4,046.86 square meters.
The acre unit is part of the imperial system of measurement and is primarily used to measure land. A single acre is about the same size as a soccer field. It can also be compared to the size of 16 tennis courts or 75 percent of a football field. The size of an acre has its beginnings in the medieval measurement of the amount of land an oxen team could plow in a day.