# Acres to hectares converter

> Convert acres to hectares (acres to hectares) with the exact factor, a conversion chart and worked steps.

Interactive version: https://www.calcopenly.com/conversion/acres-to-hectares
Subject: Unit converters

An acreage describes land area, not its shape or boundary length. The same acreage can have many different perimeters. Convert the recorded parcel area when comparing land listings, and consult the survey itself for legal boundaries or historical measurement conventions.

One acre is exactly 0.4046856422 hectares, so 10 ac is 4.046856 ha. To convert acres to hectares, multiply by 0.4046856422; to convert back, multiply by 2.4710538147.

The international acre is exactly 43,560 square feet, which is 4,046.8564224 m². Because both units are defined exactly, the factor above is exact and the results here carry no conversion error.

## Inputs

- **Acres (ac)**

## Results

- Hectares (ha) — main result
- Conversion
- 1 ha in acres (ac)

## Formula

$$
\text{hectares} = \text{acres} \times 0.40468564224
$$

## Worked examples

### 10 ac to ha

- Acres (ac): 10 ac
- **Hectares: 4.0468564224 ha**
- Checked against: Exact-fraction computation from the legal unit definitions (scripts/gen-pairs.py, Python fractions)

### 1 ac to ha

- Acres (ac): 1 ac
- **Hectares: 0.40468564224 ha**
- Checked against: Exact-fraction computation from the legal unit definitions (scripts/gen-pairs.py, Python fractions)

### 100 ac to ha

- Acres (ac): 100 ac
- **Hectares: 40.468564224 ha**
- Checked against: Exact-fraction computation from the legal unit definitions (scripts/gen-pairs.py, Python fractions)

## Questions

### When would I convert acres to hectares?

An acreage describes land area, not its shape or boundary length. The same acreage can have many different perimeters. Convert the recorded parcel area when comparing land listings, and consult the survey itself for legal boundaries or historical measurement conventions.

### How many hectares are in a acre?

One acre is exactly 0.4046856422 hectares. The international acre is exactly 43,560 square feet, which is 4,046.8564224 m².

### How do you convert acres to hectares?

Multiply the number of acres by 0.4046856422. For example, 10 ac × 0.4046856422 = 4.046856 ha. To go the other way, divide by 0.4046856422.

### How can I estimate acres to hectares without a calculator?

Multiply by 0.4. That is 1.2% low of the exact factor 0.4046856422, so 10 ac comes out as 4 ha instead of 4.0469.

### How accurate is the acres to hectares converter?

Accuracy depends on your inputs and the method's assumptions. Decimal arithmetic uses 50 significant digits, but estimates, numerical methods and source data can be less precise; the displayed rounding does not remove those limits. It is checked against 3 worked examples whose answers come from independent sources; for example, “10 ac to ha” is checked against Exact-fraction computation from the legal unit definitions (scripts/gen-pairs.py, Python fractions).

### Where does the method come from?

NIST SP 811 (2008), Guide for the Use of the International System of Units, Appendix B; NIST Handbook 44, Appendix C: General tables of units of measurement; BIPM, The International System of Units (SI Brochure), 9th edition.

## Sources

- [NIST SP 811 (2008), Guide for the Use of the International System of Units, Appendix B](https://www.nist.gov/pml/special-publication-811)
- [NIST Handbook 44, Appendix C: General tables of units of measurement](https://www.nist.gov/pml/weights-and-measures/publications/nist-handbooks/handbook-44)
- [BIPM, The International System of Units (SI Brochure), 9th edition](https://www.bipm.org/en/publications/si-brochure)