How to Convert Square miles to Square kilometres (sq mi to km²)
Area conversions are everyday maths in Singapore property: HDB flats are listed in square metres while condo listings and PSF prices use square feet. This guide shows how to convert square miles into square kilometres by hand, with examples and a quick-reference table.
The conversion
To convert square miles to square kilometres, multiply the value by 2.5899881103. To go the other way, divide by the same number (or multiply by 0.3861021585). For a quick estimate, multiply by about 2.6.
Square kilometres = square miles × 2.5899881103
Worked examples
- 3 sq mi = 7.77 km²
- 12.5 sq mi = 32.3749 km²
- 75 sq mi = 194.2491 km²
Square miles to Square kilometres table
| Square miles | Square kilometres |
|---|---|
| 1 sq mi | 2.59 km² |
| 2 sq mi | 5.18 km² |
| 5 sq mi | 12.9499 km² |
| 10 sq mi | 25.8999 km² |
| 20 sq mi | 51.7998 km² |
| 25 sq mi | 64.7497 km² |
| 50 sq mi | 129.4994 km² |
| 100 sq mi | 258.9988 km² |
| 250 sq mi | 647.497 km² |
| 500 sq mi | 1,294.99 km² |
| 1,000 sq mi | 2,589.99 km² |
Common questions
Is sq mi to km² exact?
The factors used here are the internationally defined values where they exist; results are rounded for display only.
How do I convert back?
Use the Square kilometres to Square miles converter.
Mistakes to avoid
Forgetting squared and cubed units
Area and volume factors are the length factor squared or cubed, so 1 m² is about 10.76 sq ft, not 3.28.
Multiplying when you should divide
Converting to a smaller unit gives a bigger number, and converting to a larger unit gives a smaller one. If your answer moves the wrong way, you have inverted the factor.
Rounding the factor too early
Using 3 instead of 3.28 for feet per metre introduces an error of almost 9% before you have started.
Background
Unit conversion is simply multiplication by a fixed ratio. The ratio between two units of the same quantity never changes, so once you know it you can convert any value in either direction.
Singapore adopted the metric system in the 1970s, replacing imperial units and traditional Chinese measures in most official uses. Metric units are now standard in schools, trade and government, but older units survive in property, markets and imported goods.
Writing the units next to every number while you work is the simplest way to avoid mistakes. If the units do not cancel to leave the one you want, the calculation is set up wrongly.
For any value, use the Square miles to Square kilometres Converter or browse all area converters.
Run your own numbers: Square miles to Square kilometres Converter