Square Kilometers to Square Miles Converter

Where 0.386102 comes from

This is an area conversion, not a length conversion, so the factor is the square of the linear km-to-mile ratio. One kilometer equals 0.621371 miles; squaring that gives 0.621371² ≈ 0.386102. Squaring the factor (rather than reusing the linear 0.621371 figure directly) is the detail people most often get wrong when converting areas by hand.

Worked example

A 10 km² nature reserve: 10 × 0.386102 = 3.86102, displayed as 3.861020 square miles. For a country-scale figure — 100 km² — the same factor applies: 100 × 0.386102 = 38.6102 square miles.

Why you can't just convert the side length

It's tempting to convert a single side of a square using the linear factor and assume the area conversion is the same — it isn't. A 1 km × 1 km square (1 km²) has sides equal to 0.621371 miles, but its area is 0.621371 × 0.621371 = 0.386102 square miles, not 0.621371 square miles. Any area conversion between two linear units requires squaring the linear factor.