A square mile (symbol mi²) is an imperial unit which is the area of a square whose side is one mile (or 5,280 feet). A square mile is equal to 27,878,400 square feet, 640 acres, or roughly 2½ square kilometers (2.589988 km², to be more exact).

See also: Conversion of units

In England, the Square Mile is a traditional name for the City of London.