Convert Acres to Square Miles (ac to mi2)
1 acre (ac) = 0.0015625 square miles (mi²). 1 mi² = 640 ac. Example: 15 ac = 15 × 0.0015625 = 0.0234375 mi².
Also searched as acres to mi2, acres in mi2, acres into square miles, ac to mi2, ac in square miles, ac into square mile, acre to square mile, ac to square miles converter and how many square miles in an acre.
1 ac = 0.0015625 mi²
Type in either box. Scientific notation works: 1.5e-3.
Converting a list? Use the bulk acre to square mile converter to paste a column from Excel.
How to Convert Acre to Square Mile
- 1 ac = 0.0015625 mi²
- 1 mi² = 640 ac
- Example: convert 15 ac to mi²: 15 ac = 15 × 0.0015625 mi² = 0.0234375 mi²
Formula
mi² = ac ÷ 640
Derivation from SI units:
- 1 acre = 43 560 ft² = 4 046.856 422 4 m² (international foot; the US survey foot was retired at the end of 2022)
- 1 mi² = (1609.344 m)² = 2 589 988.110336 m² = 640 acres
- 1 ac = 4046.8564224 m² ÷ 2589988.110336 m² per mi² = 0.0015625 mi²
Both units are defined exactly, so the factor is exact. Acre definition: acre; Square Mile definition: square mile.
Worked examples
- A reading of 2 ac converts to 0.003125 mi².
2 ac × 0.0015625 = 0.003125 mi² - A value of 20 ac is 0.03125 mi².
20 ac × 0.0015625 = 0.03125 mi²
Acre to Square Mile conversion table
| Acres (ac) | Square Miles (mi²) |
|---|---|
| 0.1 ac | 0.00015625 mi² |
| 0.25 ac | 0.000390625 mi² |
| 0.5 ac | 0.00078125 mi² |
| 1 ac | 0.0015625 mi² |
| 2 ac | 0.003125 mi² |
| 2.47105 ac | 0.003861015625 mi² |
| 5 ac | 0.0078125 mi² |
| 10 ac | 0.015625 mi² |
| 20 ac | 0.03125 mi² |
| 40 ac | 0.0625 mi² |
| 100 ac | 0.15625 mi² |
| 160 ac | 0.25 mi² |
| 640 ac | 1 mi² |
Where it's used
Acres are used for US, UK and Indian land and property listings, while square miles appear in US city and county areas. Both measure area, so the conversion is a fixed factor.
Acre to other area units
| Conversion | 1 ac equals |
|---|---|
| acre to square mile | 0.0015625 mi² |
| acre to square meter | 4046.856422 m² |
| acre to square centimeter | 40468564.22 cm² |
| acre to square foot | 43560 ft² |
| acre to square inch | 6272640 in² |
| acre to hectare | 0.4046856422 ha |
| acre to square millimeter | 4046856422 mm² |
| acre to square kilometre | 0.004046856422 km² |
Show 1 more units
| acre to square yard | 4840 yd² |
|---|
Frequently asked questions
How many square miles are in 1 acre?
1 ac = 0.0015625 mi².
How do I convert acres to square miles?
Multiply the value in ac by 0.0015625, or divide it by 640. For example, 15 ac × 0.0015625 = 0.0234375 mi².
Is the ac to mi² conversion exact?
Yes. Both units are defined exactly, and 1 ac is exactly 0.0015625 mi².
Sources
- NIST Handbook 44, Appendix C: General Tables of Units of Measurement, National Institute of Standards and Technology , Appendix C, units of area.
- Guide for the Use of the International System of Units (SI), NIST Special Publication 811, 2008 Edition, National Institute of Standards and Technology , Appendix B.8, "square mile (mi²)".
Last reviewed: . Factors are stored exactly and computed with 50-digit decimal arithmetic. See how we verify conversion factors.
Cite this page
APA
Scientific Converters. (2026, October 15). Convert Acres to Square Miles (ac to mi2). Retrieved October 25, 2026, from https://scientificconverters.com/area/acres-to-square-miles/
IEEE
Scientific Converters, "Convert Acres to Square Miles (ac to mi2)," scientificconverters.com. Accessed: Oct. 25, 2026. [Online]. Available: https://scientificconverters.com/area/acres-to-square-miles/