Square Kilometers to Square Miles
Convert square kilometers (km²) to square miles (mi²). Both measure surface measurement, and the conversion comes up in real estate, farming, construction work.
The Formula
``
square miles = square kilometers × 0.386102158542
square kilometers = square miles × 2.58998811034
`
One square kilometer is 0.386102 square miles, and one square mile is 2.59 square kilometers.
Conversion Table
| 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 |
The Other Direction
| 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 |
What Each Unit Is
Square Kilometers (km²) — one million square metres. The metric unit for regions, cities and land cover.
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.
A Sense of Scale
Central Park is 3.4 km²- Manhattan is 59 km²
- Greater London is 1,572 km²
- A survey township is 36 square miles
- San Francisco is 47 square miles
Doing It in Your Head
Multiply by 5, then divide by 13. 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 3.861 mi² 3.8462 mi² 38.6102 mi² 38.4615 mi²
Precision
The factor 0.386102158542 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 squareKilometerToSquareMile = (value) => value * 0.386102158542;
``
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 km² with the factor truncated at each decimal place:
| Decimals kept | Factor | 137 km² becomes | Error |
|---|---|---|---|
| 0 | 0 | 0 | 100.0000% |
| 1 | 0.4 | 54.8 | 3.5995% |
| 2 | 0.39 | 53.43 | 1.0095% |
| 3 | 0.386 | 52.882 | 0.0265% |
| 4 | 0.3861 | 52.8957 | 0.0006% |
The right number of significant figures is set by your input, not by the converter. If you measured square kilometers to three significant figures, the answer in square miles is only good to three — writing more digits claims precision the measurement never had.