The square mile (abbreviated as sq mi and sometimes as mi2) is an imperial and US unit of measure for an area equal to the area of a square of one statute mile.[1] It should not be confused with miles square, which refers to the number of miles on each side squared. For instance, 20 miles square (20 × 20 miles) is equal to 400 square miles.
One square mile is equivalent to:
When applied to a portion of the earth's surface, which is curved rather than flat, "square mile" is an informal synonym for section.