Home › Unit Conversion › Square miles to Square kilometers
Square miles to Square kilometers (mi² to km²)
Convert square miles to square kilometers: 1 mi² = 2.58999 km². Exact conversion factor, formula, 22-row table and worked examples, with JSON API and MCP access.
Formula
1 mi² = 2.58999 km²
square kilometers = square miles × 2.58998811 — reverse: square miles = square kilometers × 0.3861021585
The factor is derived from the SI definitions of both units (base unit: m2) as listed in NIST SP 811; results on this page are shown to 6 significant figures, the API returns up to 12.
Worked examples
- 5 mi² = 12.9499 km²
- 12.5 mi² = 32.3749 km²
- 100 mi² = 258.999 km²
Square miles to square kilometers conversion table
| Square miles (mi²) | Square kilometers (km²) |
|---|---|
| 1 | 2.58999 |
| 2 | 5.17998 |
| 3 | 7.76996 |
| 4 | 10.36 |
| 5 | 12.9499 |
| 6 | 15.5399 |
| 7 | 18.1299 |
| 8 | 20.7199 |
| 9 | 23.3099 |
| 10 | 25.8999 |
| 15 | 38.8498 |
| 20 | 51.7998 |
| 25 | 64.7497 |
| 30 | 77.6996 |
| 40 | 103.6 |
| 50 | 129.499 |
| 75 | 194.249 |
| 100 | 258.999 |
| 200 | 517.998 |
| 250 | 647.497 |
| 500 | 1294.99 |
| 1000 | 2589.99 |
FAQ
How many square kilometers are in one square mile?
1 mi² = 2.58999 km². The factor comes from the SI definitions of both units (NIST SP 811 / BIPM), so it is exact or correct to at least 10 significant figures.
What is the formula to convert square miles to square kilometers?
Multiply the value in square miles by 2.58998811: square kilometers = square miles × 2.58998811. For example, 5 mi² = 12.9499 km².
How do I convert square kilometers back to square miles?
Multiply by the inverse factor 0.3861021585 (square miles = square kilometers × 0.3861021585), or use the square kilometers-to-square miles page.
Related conversions
Machine access
- API:
GET https://tttkmbb.com/api/v1/convert?value=5&from_unit=mi2&to_unit=km2 - MCP: server
https://tttkmbb.com/mcp, toolconvert_unitswith{"value":5,"from_unit":"mi2","to_unit":"km2"} - Markdown: https://tttkmbb.com/conversion/square-miles-to-square-km.md · JSON: https://tttkmbb.com/conversion/square-miles-to-square-km.json (add
?value=for a result) · Units: /api/v1/units?quantity=area - OpenAPI operationId:
convert_units. Freshness:static. Authentication: none.