square mile to acre
Convert square mile (mi²) to acre (ac). Use an editable area converter, conversion formula, and reference table.
1 mi² = 640 ac
Conversion formula
One square mile equals 640 acre. Multiply your value in square mile by this factor to get acre. For the reverse conversion, divide by the same factor.
Worked example
To convert 5 square mile:5 × 640 = 3,200 ac
Conversion table
| square mile (mi²) | acre (ac) |
|---|---|
| 0.01 | 6.4 |
| 0.1 | 64 |
| 1 | 640 |
| 2 | 1,280 |
| 5 | 3,200 |
| 10 | 6,400 |
| 25 | 16,000 |
| 50 | 32,000 |
| 100 | 64,000 |
| 1000 | 640,000 |
About these measurements
Area measures a surface in two dimensions.
The base reference used here is the square meter. One square mile is 2,589,988.11 base units; one acre is 4,046.856422 base units.
Important distinctions
Square a length factor to convert an area. Units with equal factors can have different conventional uses.
Precision
The converter uses stored conversion factors and floating-point arithmetic. Results display up to ten significant digits, switching to scientific notation for very small or large values. Keep the precision of your original measurement when reporting results.
Common questions
How do I convert mi² to ac?
Multiply the quantity in mi² by 640. You can also type the value into the converter above.
Can I reverse the conversion?
Yes. Use the swap button or open the acre to square mile converter.
Reference
NIST Guide to the SI — conversion factors and prefix conventions. SI prefixes scale units by powers of ten; the dimension-specific notes above describe the assumptions used on this page.
