Definition of Square Kilometer

Square kilometre (U.S. spelling: Square kilometer), symbol km², is an SI unit of surface area. It is one of the SI derived units.

Note: "km²" means square kilometre and not kilo–square metre. For example, 3 km² is equal to 3 000 000 m² and not to 3000 m² (nor even 9 000 000 m²). Thus, in the case of an area, the SI prefixes provide steps of a factor one million instead of one thousand. As a result large numbers may be needed, even if the prefixes are fully used.