# Hectares to Acres (ha to acre)

> Convert hectares to acres: 1 ha = 2.47105 acre. Exact conversion factor, formula, 22-row table and worked examples, with JSON API and MCP access.

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

## Formula

- `1 ha = 2.47105 acre`
- `acres = hectares × 2.471053815`
- Reverse: `hectares = acres × 0.4046856422`

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 ha = 12.3553 acre
- 12.5 ha = 30.8882 acre
- 100 ha = 247.105 acre

## Conversion table

| Hectares (ha) | Acres (acre) |
| --- | --- |
| 1 | 2.47105 |
| 2 | 4.94211 |
| 3 | 7.41316 |
| 4 | 9.88422 |
| 5 | 12.3553 |
| 6 | 14.8263 |
| 7 | 17.2974 |
| 8 | 19.7684 |
| 9 | 22.2395 |
| 10 | 24.7105 |
| 15 | 37.0658 |
| 20 | 49.4211 |
| 25 | 61.7763 |
| 30 | 74.1316 |
| 40 | 98.8422 |
| 50 | 123.553 |
| 75 | 185.329 |
| 100 | 247.105 |
| 200 | 494.211 |
| 250 | 617.763 |
| 500 | 1235.53 |
| 1000 | 2471.05 |

## API

- `GET https://tttkmbb.com/api/v1/convert?value=5&from_unit=ha&to_unit=acre` → 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":"ha","to_unit":"acre"}`
- 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 acres are in one hectare?**

1 ha = 2.47105 acre. 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 hectares to acres?**

Multiply the value in hectares by 2.471053815: acres = hectares × 2.471053815. For example, 5 ha = 12.3553 acre.

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

Multiply by the inverse factor 0.4046856422 (hectares = acres × 0.4046856422), or use the acres-to-hectares page.

## Related conversions

- [Acres to hectares](https://tttkmbb.com/conversion/acres-to-hectares.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)