How to convert square feet to acres
Useful when expressing a property or site area in acres. CalcOS converts through the square meter using exact squared length definitions.
ac = ft² × 0.0000229568411387
Worked example: 43560 ft² = 1 ac.
Square Feet to Acres conversion table
| square foot (ft²) | acre (ac) |
|---|---|
| 1 | 0.0000229568411387 |
| 2 | 0.0000459136822773 |
| 5 | 0.000114784205693 |
| 10 | 0.000229568411387 |
| 25 | 0.000573921028466 |
| 100 | 0.00229568411387 |
Why area factors are squared
A square foot is a square measuring one foot on each side. Because one foot equals exactly 0.3048 meter, one square foot equals 0.3048², or exactly 0.09290304 square meter. Applying the unsquared length factor would produce the wrong area.
Acre definition
One acre equals exactly 43,560 square feet. CalcOS uses the international foot, not the retired U.S. survey foot, for contemporary conversion.
Related area conversion
Sources: BIPM SI Brochure and NIST Handbook 44, Appendix C. See the complete Area Converter guide.