Acres and hectares
The international acre is exactly 4,046.8564224 square meters, or 43,560 square feet (one chain by one furlong). Land and property lots in the US, UK, Canada and Australia are sold by the acre.
The hectare is a square 100 m on each side: exactly 10,000 square meters. Farmland, forests and large building plots are measured in hectares outside the US and UK.
Worked example
Convert 50 ac: 50 × 0.40468564224 = 20.23428211, so 50 acres is 20.23428211 hectares. Likewise 20 ac = 8.093712845 ha.
Estimating in your head
Divide by 2.5 for a quick figure; it is off by about 1.2%. For 50 ac that gives 20 ha, against 20.2343 exactly.
Going the other way
To convert hectares to acres, divide by 0.40468564224 (or multiply by 2.47105381467). The swap button between the boxes opens that page.
How this works
ha = ac × 0.40468564224
1 ac = 4,046.8564224 m² and 1 ha = 10,000 m², both by definition, so the factor is their ratio: 0.40468564224 exactly. Results drop binary floating-point noise beyond 15 significant digits and display at the precision you choose (6 significant figures by default). Copy result copies the full value.
Frequently asked
How many hectares are in a acre?
1 acre = 0.40468564224 hectares, exactly. The value follows from the unit definitions, so it never changes.
How do I convert acres to hectares?
Multiply by 0.40468564224. For example, 20 ac × 0.40468564224 = 8.093712845 ha.
What is 100 ac in hectares?
100 ac = 40.46856422 ha. The table next to the converter lists more common values.
Is the result rounded?
Only on screen. The page computes with the exact definitions and removes floating-point noise past 15 significant digits; pick 3 to 12 significant figures, or use Copy result for the full value.
Sources
- NIST SP 811 Appendix B.8 — Factors for units listed alphabetically
- Federal Register 59-5442 (1959) — Refinement of values for the yard and the pound
- Wikipedia — Acre
Reviewed Oct 17, 2026 · test vectors fixtures/units/area/acres-to-hectares/