This converter switches between square kilometers (km²) and square miles (mi²) in both directions — useful for comparing land areas, city sizes, and map measurements across metric and imperial systems. Type into either field and the other updates live.
How it works
The conversion uses one exact factor: 1 square mile = 2.589988110336 km².
- km² to mi²: square miles = km² ÷ 2.589988
- mi² to km²: square kilometers = mi² × 2.589988
That factor is the square of the linear mile-to-kilometer ratio. One mile is exactly 1.609344 km, and since area scales with length squared, 1.609344² = 2.589988110336.
The common mistake: confusing the linear and area factors
When converting kilometers to miles (a linear distance), you divide by 1.609344. When converting square kilometers to square miles (an area), you divide by 2.589988 — the squared version of the same factor. This trips people up constantly. For example, a city described as “20 km wide” covers roughly 12.4 miles linearly, but a city described as having a “400 km² footprint” covers roughly 154 square miles, not 248 (which you would get if you wrongly divided by 1.609344).
Examples across practical scales
Convert a 500 km² national park:
500 ÷ 2.589988 ≈ 193.05 mi²
Going the other way, 50 mi² is 50 × 2.589988 ≈ 129.5 km².
| Area | km² | mi² | Notes |
|---|---|---|---|
| Central Park, New York | ~3.4 km² | ~1.3 mi² | Urban park |
| Greater London | ~1,572 km² | ~607 mi² | Often cited in urban comparisons |
| 1 square mile | 2.589988 km² | 1.0 mi² | The base factor |
| 100 km² | 100 km² | 38.61 mi² | Handy round-number anchor |
When you encounter this in practice
Reading international geography. Country and city areas in Wikipedia are typically in km², while US sources often quote mi². Pasting the km² figure here gives you the mi² equivalent immediately.
Comparing national park sizes. The US National Park Service quotes park areas in acres and square miles; most international conservation databases use hectares and km². Converting between the two lets you compare a park in Scotland to one in Utah on equal footing.
Maps and GIS work. Satellite imagery tools like Google Earth report measured areas in km² by default, while many American planning documents use square miles. If you are writing a report that mixes both, the converter keeps the figures consistent.
Real-estate development. Land parcels described in km² in planning documents sometimes need to be expressed in mi² for US investors or vice versa. At the scales involved — a few km² — the difference between using the linear and area factors would misstate the parcel by nearly 40%.
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