Square kilometre (U.S. spelling: Square kilometer), symbol km², is an SI unit of surface area. It is one of the SI derived units.
1 km² is equal to:
- 1 m² = 0.000 001 km2
- 1 hectare = 0.01 km2
- 1 square mile = 2.589 988 km2
- 1 acre = 0.004 047 km2
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.
The 1 E6 m² orders of magnitude page gives comparisons with geographic areas.
hectare « square kilometre « square megametre