Square Miles to Square Kilometers

Square miles and 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.

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.

Worked example

Convert 25 mi²: 25 × 2.58998811 = 64.74970276, so 25 square miles is 64.74970276 square kilometers. Likewise 20 mi² = 51.79976221 km².

Estimating in your head

Multiply by 2.6 for a quick figure; it is off by about 0.4%. For 25 mi² that gives 65 km², against 64.7497 exactly.

Going the other way

To convert square kilometers to square miles, divide by 2.58998811 (or multiply by 0.386102158542). The swap button between the boxes opens that page.

km² = mi² × 2.58998811

1 mi² = ≈ 2,589,988.11 m² and 1 km² = 1,000,000 m², both by definition, so the factor is their ratio: 2.58998811 (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.