Square Miles to Square km Converter

One square mile is about 2.59 km². Country and state areas are often given in one and compared in the other.

How to use the Square Miles to Square km Converter

1. Type the number of square miles into the Square miles field. Decimals such as 0.5 are fine.
2. Read the answer in Square kilometres – it updates as you type, with no button to press.
3. To convert the other way, type into Square kilometres and the square miles are recalculated.
4. Press Copy results to copy both values with the page title, or Copy link to share this exact conversion.

This page converts only mi² ⇄ km². Need a different unit? Use the general area converter, where you can choose any “from” and “to” unit.

How it works

Both units measure area, so they are always in the same ratio: one square mile equals 2.5899881 square kilometres. The calculator multiplies the number of square miles you type by 2.5899881 to give square kilometres, and when you type into the square kilometres field it divides by the same factor to give square miles. Because the ratio never changes, doubling the square miles always doubles the square kilometres. Results are calculated at full precision and rounded only for display (up to eight decimal places, with very large or small values shown in scientific notation).

How to convert square miles to square kilometres

1. Write down the value in square miles, for example 1 mi².
2. Multiply by the conversion factor 2.5899881 (because 1 square mile = 2.5899881 km²).
3. 1 × 2.5899881 = 2.5899881 km².
4. To go back from square kilometres to square miles, divide by 2.5899881 – or multiply by 0.38610216.

mi² to km² conversion table

What is a square mile?

A square mile is 640 acres, about 2.59 km². U.S. land surveys divide land into one-square-mile sections, and U.S. state and county areas are given in square miles.

What is a square kilometre?

A square kilometre is a million square metres, or 100 hectares. Areas of cities, countries, lakes and national parks are reported in km².

Quick mental conversion

For a fast estimate, multiply square miles by about 2.6 to get square kilometres; the error is about 0.4%. Use the calculator above when you need the exact figure.

Common mistakes to avoid

Converting area with a length factor (1 m = 3.28 ft, but 1 m² = 10.76 ft², not 3.28 ft²), and assuming regional land units such as marla, bigha or katha have one standard size everywhere.