Square Miles to Square KM Converter
Convert square miles to square kilometres — multiply by 2.59. Results update as you type; exact factors shown.
One square mile is 2.59 square kilometres — see the exact factor, not a rounded rule of thumb.
How the square miles to square km 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.
Australia is fully metric under the National Measurement Act 1960; imperial units appear only in trade with the US and in older documents.
Common area conversions
| From | To | Units |
|---|---|---|
| 1 mi² | 2.59 km² | square mile to square kilometres |
| 2 mi² | 5.18 km² | square miles to square kilometres |
| 5 mi² | 12.9499 km² | square miles to square kilometres |
| 10 mi² | 25.8999 km² | square miles to square kilometres |
| 25 mi² | 64.7497 km² | square miles to square kilometres |
| 50 mi² | 129.4994 km² | square miles to square kilometres |
| 100 mi² | 258.9988 km² | square miles to square kilometres |
| 250 mi² | 647.497 km² | square miles to square kilometres |
| 500 mi² | 1,294.9941 km² | square miles to square kilometres |
| 1,000 mi² | 2,589.9881 km² | square miles to square kilometres |
| 5,000 mi² | 12,949.9406 km² | square miles to square kilometres |
| 50,000 mi² | 129,499.4055 km² | square miles to square kilometres |
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 km² in a square mile?
2.58999.
Why is it not 1.61?
Because area scales with the square of the length ratio.
How many acres in a square mile?
640.
How big is a national park?
Yellowstone is 3,468 square miles, about 8,983 km².
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 Measurement Institute (NMI) — Australia's national measurement authority.
Last checked: September 2026. Conversion factors are fixed by definition and do not change with tax years or regulations.