This converter turns square miles into hectares instantly, using the exact factor 1 square mile = 258.998811 hectares. Type any number and the result updates as you go — nothing is sent to a server, so the arithmetic happens entirely in your browser.
The unit for counties, national parks and weather systems in the US and UK. Ten thousand square metres, the international unit of land area.
Because the relationship is a simple proportion, one multiplication does the whole job. The table further down gives pre-computed values for the amounts people look up most often, and the result panel also reports the reverse conversion so you can check the figure both ways.
The formula
square miles- The amount you are converting, measured in square miles
258.998811- The exact number of hectares in one square mile
hectares- The converted result
How it works, step by step
- Enter the number of square miles you want to convert.
- The value is multiplied by 258.998811, the exact conversion factor.
- The result is displayed in hectares, rounded for readability.
- The unrounded value and the reverse conversion appear underneath so you can verify it.
Worked examples
Converting 5 square miles
Multiply 5 by 258.99881. That gives 1,294.99 hectares. A quick sanity check: one square mile is larger than one hectare, so the number should get bigger — and it does.
Converting 72 square miles
72 × 258.99881 = 18,647.91 hectares. Working backwards, 18,647.91 ÷ 258.99881 returns 72 square miles, which confirms the factor is applied the right way round.
How to read your score
Frequently asked questions
How many hectares are in one square mile?
Exactly 258.998811. Every conversion on this page is that single number multiplied by your input, so the result carries no rounding error beyond what is shown.
What is the formula to convert square miles to hectares?
Hectares = square miles × 258.998811. To reverse it, divide instead: square miles = hectares ÷ 258.998811, which is the same as multiplying by 0.003861021585.
Is the square mile bigger than the hectare?
Yes. One square mile equals 258.999 hectares, so it is the larger unit.
Why does my answer differ slightly from other square-miles to hectares converters?
Most differences come from rounding the factor too early. This tool keeps full double precision through the calculation and only rounds at the final display step, and it also shows the unrounded value so you can see exactly where any difference appears.
What is a square mile?
The unit for counties, national parks and weather systems in the US and UK.
What is a hectare?
Ten thousand square metres, the international unit of land area.
Square Miles to hectares reference table
| Square Miles | Hectares |
|---|---|
| 0.5 mi² | 129.4994 ha |
| 1 mi² | 258.9988 ha |
| 2 mi² | 517.9976 ha |
| 3 mi² | 776.9964 ha |
| 5 mi² | 1,294.99 ha |
| 10 mi² | 2,589.99 ha |
| 15 mi² | 3,884.98 ha |
| 20 mi² | 5,179.98 ha |
| 25 mi² | 6,474.97 ha |
| 50 mi² | 12,949.94 ha |
| 75 mi² | 19,424.91 ha |
| 100 mi² | 25,899.88 ha |
| 250 mi² | 64,749.7 ha |
| 500 mi² | 129,499.41 ha |
| 1000 mi² | 258,998.81 ha |
Exact factor: 1 square mile = 258.998811 hectares. Values rounded for display.