Acres to Hectares
Convert acres to hectares. A hectare is exactly 10,000 square metres; the acre is not exact, and this page says which acre it uses.
ha = ac × 4046.873 ÷ 10000
NIST SP 811 (2008), Appendix B.8 — acre (based on U.S. survey foot) to square meter (m2) = 4.046 873 E+03
Land is bought in acres in some countries and hectares in others, and the two are close enough to be confused and far enough apart to matter: a hectare is about two and a half acres. The hectare is the tidy one — exactly ten thousand square metres, a square a hundred metres on a side. The acre is not tidy at all. It is a survey unit inherited from ploughing, and the figure NIST publishes for it is rounded rather than exact, which is why this page shows it as rounded instead of pretending otherwise.
How it is calculated
ha = ac × 4046.873 ÷ 10000
The acre goes to square metres first, then to hectares. The 4046.873 is the value for the acre based on the U.S. survey foot, and NIST prints it rounded — so the result is accurate to seven figures rather than exact, and the tool marks it that way.
Common values
| acres | hectares |
|---|---|
| 1 | 0.4046873 |
| 2 | 0.8093746 |
| 2.5 | 1.0117183 |
| 5 | 2.0234365 |
| 10 | 4.046873 |
| 20 | 8.093746 |
| 40 | 16.187492 |
| 50 | 20.234365 |
| 100 | 40.46873 |
| 250 | 101.17183 |
| 640 | 258.99987 |
Questions people ask
- How many acres are in a hectare?
- About 2.471. The reverse figure, that an acre is about 0.4047 hectares, is the one worth remembering because it is easier to multiply in your head.
- Is there more than one acre?
- Yes, and it is the reason this page names its source. The international acre and the U.S. survey acre differ by about four parts in a million — irrelevant for a garden, but on a ranch of ten thousand acres it is roughly a fortieth of an acre.
- What does an acre look like?
- A rectangle of 66 by 660 feet, which is one chain by one furlong. That shape is not an accident: it is the area a team of oxen was reckoned to plough in a day, and the long thin form is how ploughing actually went.
- Why is a square mile 640 acres?
- Because the survey grid was laid out that way. A section is one square mile and divides evenly into quarter sections of 160 acres, which is where the shape of a lot of farmland comes from.
Related tools
Hectares to Acres
Convert hectares to acres. The hectare is exact, the acre is not, and the result is marked as rounded rather than presented as exact.
Square Feet to Square Meters
Convert square feet to square meters exactly. A square foot is 0.09290304 square meters, which follows from the foot being exactly 0.3048 metres.
Kilometers to Miles
Convert kilometers to miles instantly in your browser. One mile is exactly 1.609344 kilometers, the factor fixed by the international yard and pound agreement.
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