# Square kilometre

decimal multiple of the SI unit of surface area

A **square kilometer** (sometimes written * km²*) is based on the SI unit of measurement of area, the

*square meter*. It is the area inside a square that has each side equal to 1 kilometer (1000 meters). This way of talking about area is often used to say how much land there is, on a farm or in a city, for example.

One square kilometer is just less than 0.39 square miles.