Square Miles to Square Kilometers
Convert square miles (mi²) to square kilometers (km²). Both measure surface measurement, and the conversion comes up in real estate, farming, construction work.
The Formula
``
square kilometers = square miles × 2.58998811034
square miles = square kilometers × 0.386102158542
`
One square mile is 2.59 square kilometers, and one square kilometer is 0.386102 square miles.
Conversion Table
| Square Miles | Square Kilometers |
|---|---|
| 1 mi² | 2.59 km² |
| 2 mi² | 5.18 km² |
| 5 mi² | 12.9499 km² |
| 10 mi² | 25.8999 km² |
| 25 mi² | 64.7497 km² |
| 50 mi² | 129.4994 km² |
| 100 mi² | 258.9988 km² |
| 500 mi² | 1,294.99 km² |
| 1,000 mi² | 2,589.99 km² |
The Other Direction
| Square Kilometers | Square Miles |
|---|---|
| 1 km² | 0.386102 mi² |
| 2 km² | 0.772204 mi² |
| 5 km² | 1.9305 mi² |
| 10 km² | 3.861 mi² |
| 25 km² | 9.6526 mi² |
| 50 km² | 19.3051 mi² |
| 100 km² | 38.6102 mi² |
| 500 km² | 193.0511 mi² |
| 1,000 km² | 386.1022 mi² |
What Each Unit Is
Square Miles (mi²) — 640 acres, or 2.589988 square kilometres. The unit of the US Public Land Survey System, which divided the west into square-mile sections.
Square Kilometers (km²) — one million square metres. The metric unit for regions, cities and land cover.
A Sense of Scale
A survey township is 36 square miles- San Francisco is 47 square miles
- Central Park is 3.4 km²
- Manhattan is 59 km²
- Greater London is 1,572 km²
Doing It in Your Head
Multiply by 13, then divide by 5. That is off by 0.39% — close enough to judge a
distance, a weight or a price, and not close enough to sign off on a drawing.
Exact Mental shortcut 25.8999 km² 26 km² 258.9988 km² 260 km²
Precision
The factor 2.58998811034 is rounded. For engineering work carry more digits than the table above, and round only at the end — rounding at each step compounds.
In Code
`javascript
const squareMileToSquareKilometer = (value) => value * 2.58998811034;
``
Where This Conversion Comes Up
- Real estate
- Farming
- Construction
- Landscaping
- Flooring
How Many Decimals Do You Need?
Rounding the factor costs accuracy, and how much depends on the factor. Converting 137 mi² with the factor truncated at each decimal place:
| Decimals kept | Factor | 137 mi² becomes | Error |
|---|---|---|---|
| 0 | 3 | 411 | 15.8306% |
| 1 | 2.6 | 356.2 | 0.3866% |
| 2 | 2.59 | 354.83 | 0.0005% |
| 3 | 2.59 | 354.83 | 0.0005% |
| 4 | 2.59 | 354.83 | 0.0005% |
The right number of significant figures is set by your input, not by the converter. If you measured square miles to three significant figures, the answer in square kilometers is only good to three — writing more digits claims precision the measurement never had.