Square Miles to Square Kilometres Converter — mi² ↔ km²
Convert between square miles and square kilometres in either direction. Fill either box for an instant result, plus equivalents in hectares, acres and square metres — all from the exact international-mile definition.
mi²
km²
km² = mi² × 2.58999 (1 mile = 1.609344 km, exact)
1 international mile = 1.609344 km (exact)
Square both sides
Multiply your area
- 1
Mile in km
1 mi = 1.609344 km → 1 mi² = 1.609344² = 2.58998811The international mile is defined as exactly 1,609.344 m. - 2
Square kilometres
1 × 2.58998811 = 2.589988
How does this calculator work?
Multiply square miles by 2.589988110336 to get square kilometres (from 1 mile = 1.609344 km exactly). One square mile also equals 640 acres and ≈ 259 hectares. The converter works in both directions — enter either mi² or km² and get the other instantly.
Formula
How this is calculated
The international mile is defined as exactly 1,609.344 metres (= 1.609344 km). Because area scales by the square of the linear dimension, one square mile equals 1.609344² = 2.589988110336 km². This is an exact value — no rounding has occurred. The reverse factor is simply the reciprocal: 1 km² = 1 ÷ 2.589988110336 ≈ 0.38610216 mi².
From square miles other large-area units follow easily: 1 square mile contains exactly 640 acres (the historical survey definition of a "section" in the US Public Land Survey System), making acres a quick sanity-check for any mi² figure. One square mile is also 259 hectares (2.59 km² × 100 ha/km²) and about 2.59 million square metres.
The converter is bidirectional: whichever field you type in is treated as the source. Common reference points: the island of Manhattan is about 23 mi² (59.5 km²); an average US county is around 1,000 mi² (2,590 km²); and a standard US "section" is exactly 1 mi² = 640 acres.
Frequently asked questions
Exactly 2.589988110336 km², derived from the international mile: 1 mile = 1,609.344 m = 1.609344 km, so 1 mi² = 1.609344² km².
Approximately 0.38610216 square miles (1 ÷ 2.589988110336). For example, 10 km² ≈ 3.861 mi².
Exactly 640 acres. This is the original US Public Land Survey definition of a "section": a township (6 mi × 6 mi = 36 mi²) is divided into 36 sections of 1 mi² = 640 acres each.
Also known as
TG we-Calculate Editorial Team. (2026). Square Miles to Square Kilometres Converter — mi² ↔ km² [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/square-miles-to-square-km-converter
TG we-Calculate Editorial Team. "Square Miles to Square Kilometres Converter — mi² ↔ km²." TG we-Calculate. 2026. https://we-calculate.com/calculator/square-miles-to-square-km-converter.
TG we-Calculate Editorial Team, "Square Miles to Square Kilometres Converter — mi² ↔ km²," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/square-miles-to-square-km-converter
@misc{wecalculate_square_miles_to_square_km_converter, title = {Square Miles to Square Kilometres Converter — mi² ↔ km²}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/square-miles-to-square-km-converter}}, year = {2026}, note = {TG we-Calculate} }
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