Square Miles to Square Kilometers Converter
Enter an area in square miles and the answer in square kilometers is displayed instantly. The guide gives the exact factor, explains why it is not the same as the length factor and offers a table of common values.
Related converters
Created by the Reeliy Editorial Team. Last updated: Oct 19, 2026
How many square kilometers are in a square mile?
One square mile equals 2.589988110336 square kilometers. The factor is exact. A mile is defined as 1.609344 kilometers, and a square mile is a square with a mile on each side, so its area is 1.609344 × 1.609344 = 2.589988110336 km2.
km2 = sq mi × 2.589988110336
For everyday use, 2.59 is plenty. The reverse factor, square kilometers to square miles, is about 0.3861.
Square miles and square kilometers compared
Both units describe large regions: counties, lakes, national parks, cities, islands. Square miles dominate in the United States and appear in British usage, while nearly everywhere else publishes areas in square kilometers.
A square mile also has handy equivalents in other land units: 640 acres, about 259 hectares, and 27,878,400 square feet. In the US public land survey a section is one square mile and a township is a block of 36 sections, which is 36 sq mi or about 93.24 km2.
How to convert square miles to square kilometers
- Type the number of square miles into the first box.
- Read the result in square kilometers from the second box.
- For a mental estimate, multiply by 2.5 and then add roughly 4% of the product.
Example 1: a county covering 14.5 sq mi is 14.5 × 2.589988110336 = 37.5548 km2.
Example 2: a 36-square-mile township converts to 36 × 2.589988110336 = 93.2396 km2.
The converter shows the answer to eight decimal places, with trailing zeros removed, so 1 sq mi appears as 2.58998811.
Square miles to square kilometers table
| Square miles | Square kilometers |
|---|---|
| 0.1 | 0.259 |
| 0.25 | 0.6475 |
| 0.5 | 1.295 |
| 1 | 2.59 |
| 2 | 5.18 |
| 5 | 12.9499 |
| 10 | 25.8999 |
| 25 | 64.7497 |
| 50 | 129.4994 |
| 100 | 258.9988 |
| 500 | 1,294.9941 |
| 1,000 | 2,589.9881 |
The most common mistake
People often multiply square miles by 1.609, the factor for miles to kilometers. That answers a different question. Because the unit is squared, the factor must be squared too: using 1.609 on 100 sq mi gives 160.9 km2, which is about 38% too low compared with the true 259.0 km2.
To go the other way use the square kilometers to square miles converter. Smaller plots are easier in acres, and the full area converter covers every other pairing.
Frequently asked questions
How many square kilometers are in a square mile?
Exactly 2.589988110336, normally rounded to 2.59.
How many square miles are in a square kilometer?
One square kilometer is about 0.3861 square miles.
How many acres are in a square mile?
A square mile contains 640 acres.
Why can I not multiply by 1.609?
1.609 converts lengths. For areas you need the square of that number, 1.609344² = 2.589988.
References
- Thompson, A. and Taylor, B. N. (2008). Guide for the Use of the International System of Units (SI), NIST Special Publication 811, 2008 edition.
- International yard and pound agreement of 1959, which fixed the international yard at exactly 0.9144 meter and therefore the mile at exactly 1.609344 kilometers.
Cite this converter and page
If you use this page in your work, you can cite it as:
Reeliy Editorial Team. (2026). Square Miles to Square Kilometers Converter. Reeliy. https://reeliy.com/converters/convert-sqmi-to-square-km-miles“Square Miles to Square Kilometers Converter.” Reeliy, 2026, https://reeliy.com/converters/convert-sqmi-to-square-km-miles.