The exact factor, and a shortcut that’s close enough
An acre is exactly 4,046.8564224 m² and a hectare is exactly 10,000 m², so the conversion factors are fixed. For a fast estimate, treat 2.5 acres as 1 hectare — multiply hectares by 2.5, or take 40% of acres. That is within about 1.2% of the exact numbers.
Quick reference
| Acres | Hectares | Hectares | Acres |
|---|---|---|---|
| 1 | 0.4047 | 1 | 2.4711 |
| 2 | 0.8094 | 2 | 4.9421 |
| 5 | 2.0234 | 5 | 12.355 |
| 10 | 4.0469 | 10 | 24.711 |
| 50 | 20.234 | 50 | 123.55 |
| 100 | 40.469 | 100 | 247.11 |
A typical suburban lot of a third of an acre is 0.135 ha; a 100-acre plantation is about 40.5 ha.
The mix-ups worth avoiding
- An acre is not close to a hectare. An acre is only 0.4 ha, so the two are not interchangeable — treating them as equal overstates a metric area by roughly 2.5 times.
- A hectare is 10,000 m², not 1,000. It is 100 ares of 100 m² each. One square kilometer holds 100 hectares.
- Hectare (ha) is area; hectometer (hm) is length. Different quantities that look alike as abbreviations.
Common questions
How many acres are in a hectare?
One hectare is 2.47105 acres. The reverse is that one acre is 0.404686 hectares. Both factors are exact, since an acre is defined as 4,046.8564224 square meters and a hectare as exactly 10,000.
What is a quick way to convert in my head?
Hectares to acres, multiply by about 2.5. Acres to hectares, divide by about 2.5, or take 40% of the number. The shortcut is under 1.2% off the exact factor.
Is a hectare bigger than an acre?
Yes, roughly two and a half times bigger. A hectare is a square 100 meters on each side, the size of an association-football pitch including run-off. An acre is a bit under half of that.
