Square Kilometers to Square Miles

Square kilometers and square miles

A square kilometer is the area of a square 1 km on each side: 1,000,000 m² or 100 hectares. Countries, cities, lakes and forests are compared in square kilometers.

A square mile is a square one international mile on each side: exactly 2,589,988.110336 m², or 640 acres. US states, counties and cities, and wildfire areas in US news, are given in square miles.

Worked example

Convert 100 km²: 100 × 0.3861021585 = 38.61021585, so 100 square kilometers is 38.61021585 square miles. Likewise 200 km² = 77.22043171 mi².

Estimating in your head

Divide by 2.6 for a quick figure; it is off by about 0.4%. For 100 km² that gives 38.5 mi², against 38.6102 exactly.

Going the other way

To convert square miles to square kilometers, divide by 0.3861021585 (or multiply by 2.58998811034). The swap button between the boxes opens that page.

mi² = km² × 0.3861021585

1 km² = 1,000,000 m² and 1 mi² = ≈ 2,589,988.11 m², both by definition, so the factor is their ratio: 0.3861021585 (rounded here; the page uses the full value). Results drop binary floating-point noise beyond 15 significant digits and display at the precision you choose (6 significant figures by default). Copy result copies the full value.