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:

• the area of a square measuring 1 kilometre on each side
• 1 000 000 m²
• 100 hectares
• 0.386 102 square miles (statute)
• 247.105 381 acres

Conversely:

• 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

See also

• Conversion of units.
• SI prefix for the precise meaning of the prefix "k"