About the mi² to ha calculation
One square mile is exactly 258.999 hectares, so converting between them is a single multiplication. Enter any value above and the result updates as you type. Used for land and territory area in the US and UK. One square mile is exactly 640 acres. Exactly 10,000 m², the metric standard for farmland and land registry.
Formula
ha = mi² × 258.999
1 mi² = 258.999 ha
1 ha = 0.00386102 mi²Worked example
To convert 1 mi², multiply by 258.999: 1 × 258.999 = 258.999 ha.
Frequently asked questions
How many hectares are in a square mile?
There are 258.999 hectares in one square mile. To convert any amount, multiply the number of square miles by 258.999.
How do I convert hectares back to square miles?
Divide instead of multiplying, or equivalently multiply by 0.00386102. One hectare is 0.00386102 square miles.
Is this conversion exact?
Yes. Since the international agreement of 1959, the relationship between square miles and hectares is defined exactly rather than measured, so the only rounding here is in how many decimal places we show.
Where is each of these units used?
Square Miles: used for land and territory area in the US and UK. One square mile is exactly 640 acres. Hectares: exactly 10,000 m², the metric standard for farmland and land registry.
Sources
- NIST Special Publication 811 — Guide for the Use of the International System of Units