Square Miles to Square Kilometers Converter
Convert square miles to square kilometers and back. 1 square mile = 2.58998811034 square kilometers (rounded).
Tip: Results show up to 8 significant digits. The factors and their sources are listed on the "Where our numbers come from" page.
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Square Miles and Square Kilometers
One square mile is about 2.58998811034 square kilometers, and one square kilometer is about 0.386102158542 square miles. The converter works both ways: use the two tabs at the top of the tool to choose the direction.
Quick conversion table
Square Miles to Square Kilometers
| Square Miles | Square Kilometers |
|---|---|
| 0.5 mi² | 1.2949941 km² |
| 1 mi² | 2.5899881 km² |
| 2 mi² | 5.1799762 km² |
| 5 mi² | 12.949941 km² |
| 10 mi² | 25.899881 km² |
| 25 mi² | 64.749703 km² |
| 50 mi² | 129.49941 km² |
| 100 mi² | 258.99881 km² |
| 250 mi² | 647.49703 km² |
| 500 mi² | 1,294.9941 km² |
| 1,000 mi² | 2,589.9881 km² |
Square Kilometers to Square Miles
| Square Kilometers | Square Miles |
|---|---|
| 1 km² | 0.38610216 mi² |
| 2 km² | 0.77220432 mi² |
| 5 km² | 1.9305108 mi² |
| 10 km² | 3.8610216 mi² |
| 25 km² | 9.652554 mi² |
| 50 km² | 19.305108 mi² |
| 100 km² | 38.610216 mi² |
| 250 km² | 96.52554 mi² |
| 500 km² | 193.05108 mi² |
| 1,000 km² | 386.10216 mi² |
Exact factor and source
| Conversion | Value | Basis |
|---|---|---|
| 1 square mile in square kilometers | 2.58998811034 | rounded to 12 digits. NIST SP 811 (2008), Appendix B.8: 1 mi2 = (1609.344 m)^2 = 2,589,988.110336 m2 exactly |
| 1 square kilometer in square miles | 0.386102158542 | rounded to 12 digits. SI Brochure, 9th edition (BIPM 2019): SI prefix kilo squared; 1 km2 = 10^6 m2 |
How to convert square miles to square kilometers
- Step oneTake the number of square miles.
- Step twoMultiply it by 2.58998811034.
- Step threeThe result is the number of square kilometers.
- Step fourTo go back, divide by 2.58998811034, or multiply by 0.386102158542.
Example: 10 mi² x 2.58998811034 = 25.8998811034 km².
All area units compared
Each unit written in square meters, the base unit of this tool. Exact values come straight from the definitions.
| Unit | Symbol | Value in square meters |
|---|---|---|
| Square meters | m² | 1 square meter |
| Square feet | ft² | 0.09290304 square meters |
| Square inches | in² | 0.00064516 square meters |
| Acres | ac | 4,046.8564224 square meters |
| Hectares | ha | 10,000 square meters |
| Square kilometers | km² | 1,000,000 square meters |
| Square miles | mi² | 2,589,988.11034 square meters |
What is a square mile?
A square mile is the area of a square one mile on each side: 2.58998811034 square kilometers or 640 acres.
What is a square kilometer?
A square kilometer (km²) is one million square meters, or 0.386102158542 square miles. Countries, lakes and cities are compared in square kilometers.
What this converter does not do
- Results are rounded for display to 8 significant digits; the stored factor is the exact one.
- It uses the international acre and foot, not the US survey versions.
- It converts areas only; it does not turn a length and a width into an area.
Frequently asked questions
How many square kilometers are in a square mile?
1 square mile is about 2.58998811034 square kilometers. The factor is rounded to 12 significant digits.
How many square miles are in a square kilometer?
1 square kilometer is about 0.386102158542 square miles.
How many square kilometers is 10 square miles?
10 square miles is 25.899881 square kilometers, or 6,400 acres.
Where do the factors come from?
Square miles: NIST SP 811 (2008), Appendix B.8: 1 mi2 = (1609.344 m)^2 = 2,589,988.110336 m2 exactly. Square kilometers: SI Brochure, 9th edition (BIPM 2019): SI prefix kilo squared; 1 km2 = 10^6 m2.
References
- Square Miles: NIST SP 811 (2008), Appendix B.8: 1 mi2 = (1609.344 m)^2 = 2,589,988.110336 m2 exactly
- Square Kilometers: SI Brochure, 9th edition (BIPM 2019): SI prefix kilo squared; 1 km2 = 10^6 m2
- NIST Special Publication 811: Guide for the Use of the International System of Units (SI), 2008 edition.
- The International System of Units (SI Brochure), 9th edition, BIPM.