How to convert square miles to square kilometres
One square mile equals 2.59 square kilometres, so multiply the number of square miles by 2.59:
km² = mi² × 2.59
mi² = km² ÷ 2.59 (1 km² = 0.386102 mi²)
Example: 10 mi² → 10 × 2.59 = 25.8999 km².
Going the other way, divide by 2.59, or multiply by 0.386102; the square kilometres to square miles converter does it for you.
Everyday values
| Square miles | Square kilometres | For example |
|---|---|---|
| 1 mi² | 2.59 km² | one square mile (640 acres) |
| 10 mi² | 25.8999 km² | 10 mi² |
| 100 mi² | 258.999 km² | 100 mi² |
When you need this conversion
One square mile is 2.59 km². Because area scales with the square of length, the factor is 1.609² rather than 1.609.
Square mile to square kilometre conversion table
| mi² | km² | mi² | km² |
|---|---|---|---|
| 1 mi² | 2.59 km² | 13 mi² | 33.6698 km² |
| 2 mi² | 5.18 km² | 14 mi² | 36.2598 km² |
| 3 mi² | 7.77 km² | 15 mi² | 38.8498 km² |
| 4 mi² | 10.36 km² | 16 mi² | 41.4398 km² |
| 5 mi² | 12.9499 km² | 17 mi² | 44.0298 km² |
| 6 mi² | 15.5399 km² | 18 mi² | 46.6198 km² |
| 7 mi² | 18.1299 km² | 19 mi² | 49.2098 km² |
| 8 mi² | 20.7199 km² | 20 mi² | 51.7998 km² |
| 9 mi² | 23.3099 km² | 21 mi² | 54.3898 km² |
| 10 mi² | 25.8999 km² | 22 mi² | 56.9797 km² |
| 11 mi² | 28.4899 km² | 23 mi² | 59.5697 km² |
| 12 mi² | 31.0799 km² | 24 mi² | 62.1597 km² |
About the units
- Square mile (mi²): 640 acres, about 2.59 km².
- Square kilometre (km²): 1,000,000 m², or 100 hectares.
Both are units of area. The conversion factor comes from the exact definitions above, so the calculator is exact; results are only rounded for display (up to six significant digits).
Frequently asked questions
How many square kilometres are in one square mile?
One square mile is 2.59 square kilometres. One square kilometre is 0.386102 square miles.
How do I convert square miles to square kilometres?
Multiply the value in square miles by 2.59. To go back, divide by 2.59.
What is 10 mi² in square kilometres?
10 mi² = 25.8999 km².
What is 100 mi² in square kilometres?
100 mi² = 258.999 km².
Sources
- NIST Special Publication 811 (2008), Guide for the Use of the International System of Units (SI), Appendix B: conversion factors.
- NIST Handbook 44 (2024), Appendix C: General tables of units of measurement.
Last reviewed 5 October 2026. Results are estimates; see our disclaimer.