# Square feet to Acres (ft² to acre)

> Convert square feet to acres: 1 ft² = 0.0000229568 acre. Exact conversion factor, formula, 22-row table and worked examples, with JSON API and MCP access.

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

## Formula

- `1 ft² = 0.0000229568 acre`
- `acres = square feet × 0.00002295684114`
- Reverse: `square feet = acres × 43560`

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 ft² = 0.000114784 acre
- 12.5 ft² = 0.000286961 acre
- 100 ft² = 0.00229568 acre

## Conversion table

| Square feet (ft²) | Acres (acre) |
| --- | --- |
| 1 | 0.0000229568 |
| 2 | 0.0000459137 |
| 3 | 0.0000688705 |
| 4 | 0.0000918274 |
| 5 | 0.000114784 |
| 6 | 0.000137741 |
| 7 | 0.000160698 |
| 8 | 0.000183655 |
| 9 | 0.000206612 |
| 10 | 0.000229568 |
| 15 | 0.000344353 |
| 20 | 0.000459137 |
| 25 | 0.000573921 |
| 30 | 0.000688705 |
| 40 | 0.000918274 |
| 50 | 0.00114784 |
| 75 | 0.00172176 |
| 100 | 0.00229568 |
| 200 | 0.00459137 |
| 250 | 0.00573921 |
| 500 | 0.0114784 |
| 1000 | 0.0229568 |

## API

- `GET https://tttkmbb.com/api/v1/convert?value=5&from_unit=ft2&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":"ft2","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 square foot?**

1 ft² = 0.0000229568 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 square feet to acres?**

Multiply the value in square feet by 0.00002295684114: acres = square feet × 0.00002295684114. For example, 5 ft² = 0.000114784 acre.

**How do I convert acres back to square feet?**

Multiply by the inverse factor 43560 (square feet = acres × 43560), or use the acres-to-square feet page.

## Related conversions

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

## 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)