The exact equivalent
An acre is 0.404686 hectares, so a hectare is 2.47105 acres. A hectare is exactly 10,000 square metres; an acre is 4,046.86.
1 acre = 0.40468564 ha
1 ha = 2.47105381 acre
How to convert it by hand
Just multiply by the conversion factor. To go from acres to hectares, multiply by 0.404686; to come back, divide by that same number or multiply by 2.471054.
For example: 25 acre × 0.404686 = 10.1171 ha.
A tip that saves mistakes: check the result goes the way you expect. If hectares are a smaller unit than acres, the number has to come out bigger. If it comes out smaller, you divided when you should have multiplied.
Conversion table
| acre | ha |
|---|---|
| 1 | 0.4047 |
| 2 | 0.8094 |
| 5 | 2.0234 |
| 10 | 4.0469 |
| 20 | 8.0937 |
| 50 | 20.2343 |
| 100 | 40.4686 |
Reference points to picture it
| Reference | Equals |
|---|---|
| 1 acre | 0.40 ha |
| A football pitch | 1.76 acres = 0.71 ha |
| A 10-acre plot | 4.05 ha |
| 1 hectare | 2.47 acres |
The trick for doing it in your head
Divide by 2.5. For 10 acres: 10 ÷ 2.5 = 4 hectares, against a true 4.05.
It is fine for getting by without a phone, but not for anything that depends on precision: in a recipe, on a building site or in a dose, use the exact conversion.