# Acres to Hectares (acre to ha)

> Convert acres to hectares: 1 acre = 0.404686 ha. Exact conversion factor, formula, 22-row table and worked examples, with JSON API and MCP access.

- Page id: `acres-to-hectares` · Quantity: Area (`area`, base unit m2) · Tool: `convert_units`
- Canonical page: https://tttkmbb.com/conversion/acres-to-hectares · This document: https://tttkmbb.com/conversion/acres-to-hectares.md · JSON: https://tttkmbb.com/conversion/acres-to-hectares.json (add `?value=` for a result)

## Formula

- `1 acre = 0.404686 ha`
- `hectares = acres × 0.4046856422`
- Reverse: `acres = hectares × 2.471053815`

The factor follows from the SI definitions of both units (NIST SP 811); values below are rounded to 6 significant figures, the API returns up to 12.

## Worked examples

- 5 acre = 2.02343 ha
- 12.5 acre = 5.05857 ha
- 100 acre = 40.4686 ha

## Conversion table

| Acres (acre) | Hectares (ha) |
| --- | --- |
| 1 | 0.404686 |
| 2 | 0.809371 |
| 3 | 1.21406 |
| 4 | 1.61874 |
| 5 | 2.02343 |
| 6 | 2.42811 |
| 7 | 2.8328 |
| 8 | 3.23749 |
| 9 | 3.64217 |
| 10 | 4.04686 |
| 15 | 6.07028 |
| 20 | 8.09371 |
| 25 | 10.1171 |
| 30 | 12.1406 |
| 40 | 16.1874 |
| 50 | 20.2343 |
| 75 | 30.3514 |
| 100 | 40.4686 |
| 200 | 80.9371 |
| 250 | 101.171 |
| 500 | 202.343 |
| 1000 | 404.686 |

## API

- `GET https://tttkmbb.com/api/v1/convert?value=5&from_unit=acre&to_unit=ha` → unified JSON envelope with `result.values.result`, `formula`, `factor`, `sources`, `freshness`
- MCP: server `https://tttkmbb.com/mcp`, tool `convert_units` with `{"value":5,"from_unit":"acre","to_unit":"ha"}`
- All area units: https://tttkmbb.com/api/v1/units?quantity=area · full converter: [Area Converter](https://tttkmbb.com/conversion/area.md)
- Authentication: none. Freshness: `static` (fixed conversion factors).

## FAQ

**How many hectares are in one acre?**

1 acre = 0.404686 ha. The factor comes from the SI definitions of both units (NIST SP 811 / BIPM), so it is exact or correct to at least 10 significant figures.

**What is the formula to convert acres to hectares?**

Multiply the value in acres by 0.4046856422: hectares = acres × 0.4046856422. For example, 5 acre = 2.02343 ha.

**How do I convert hectares back to acres?**

Multiply by the inverse factor 2.471053815 (acres = hectares × 2.471053815), or use the hectares-to-acres page.

## Related conversions

- [Hectares to acres](https://tttkmbb.com/conversion/hectares-to-acres.md) (reverse)
- [Square meters to Square feet](https://tttkmbb.com/conversion/square-meters-to-square-feet.md)
- [Square feet to Square meters](https://tttkmbb.com/conversion/square-feet-to-square-meters.md)
- [Acres to Square meters](https://tttkmbb.com/conversion/acres-to-square-meters.md)
- [Square meters to Acres](https://tttkmbb.com/conversion/square-meters-to-acres.md)
- [Square kilometers to Square miles](https://tttkmbb.com/conversion/square-km-to-square-miles.md)
- [Square miles to Square kilometers](https://tttkmbb.com/conversion/square-miles-to-square-km.md)
- [Hectares to Square meters](https://tttkmbb.com/conversion/hectares-to-square-meters.md)
- [Square meters to Hectares](https://tttkmbb.com/conversion/square-meters-to-hectares.md)

## Data Sources

- NIST Special Publication 811 – Guide for the Use of the International System of Units (SI), Appendix B conversion factors — https://www.nist.gov/pml/special-publication-811 (standard, retrieved 2026-09-24)
- BIPM – The International System of Units (SI Brochure, 9th edition) — https://www.bipm.org/en/publications/si-brochure (standard, retrieved 2026-09-24)
- Wikipedia – Conversion of units — https://en.wikipedia.org/wiki/Conversion_of_units (reference, retrieved 2026-09-24)