Square KM to Square Miles Converter
Convert square kilometres to square miles — one square mile is 2.59 km². Results update as you type; exact factors shown.
One square kilometre is 0.3861 square miles — see the exact factor, not a rounded rule of thumb.
How the square km to square miles converter works
Areas convert through the square metre. Because the inch is exactly 25.4 mm, a square foot is exactly 0.09290304 m², an acre (43,560 square feet) is exactly 4,046.8564224 m² and a square mile (640 acres) is 2,589,988.110336 m². A hectare is 10,000 m² by definition.
The UK is metric for most trade and science but keeps miles, pints, stone and mpg (with the imperial gallon) in daily life.
Common area conversions
| From | To | Units |
|---|---|---|
| 1 km² | 0.3861 mi² | square kilometre to square miles |
| 2 km² | 0.7722 mi² | square kilometres to square miles |
| 5 km² | 1.9305 mi² | square kilometres to square miles |
| 10 km² | 3.861 mi² | square kilometres to square miles |
| 25 km² | 9.6526 mi² | square kilometres to square miles |
| 50 km² | 19.3051 mi² | square kilometres to square miles |
| 100 km² | 38.6102 mi² | square kilometres to square miles |
| 250 km² | 96.5255 mi² | square kilometres to square miles |
| 500 km² | 193.0511 mi² | square kilometres to square miles |
| 1,000 km² | 386.1022 mi² | square kilometres to square miles |
| 10,000 km² | 3,861.0216 mi² | square kilometres to square miles |
| 100,000 km² | 38,610.2159 mi² | square kilometres to square miles |
Units in this converter and their exact factors
| Unit | Symbol | One unit in square metres |
|---|---|---|
| square millimetre | mm² | 0.000001 square metre |
| square centimetre | cm² | 0.0001 square metre |
| square metre | m² | 1 square metre |
| hectare | ha | 10,000 square metre |
| square kilometre | km² | 1,000,000 square metre |
| square inch | in² | 0.00064516 square metre |
| square foot | ft² | 0.09290304 square metre |
| square yard | yd² | 0.83612736 square metre |
| acre | ac | 4,046.8564224 square metre |
| square mile | mi² | 2,589,988.110336 square metre |
FAQFrequently asked questions about area conversion
How many square miles in a square km?
0.3861.
Why is it not 0.62?
Because area scales with the square: 0.6214² is 0.3861.
How big is a square mile?
640 acres, or 2.59 km².
How large is a city in km²?
Greater London is about 1,572 km², which is 607 square miles.
Where these figures come from
- BIPM — The International System of Units (SI Brochure, 9th edition) — definitions of the base and derived units.
- NIST Special Publication 811 — Guide for the Use of the International System of Units — the exact conversion factors used here.
- National Physical Laboratory (NPL) — United Kingdom's national measurement authority.
Last checked: September 2026. Conversion factors are fixed by definition and do not change with tax years or regulations.