Square Miles to Acres
A square mile is 640 acres, used to describe the area of cities, counties, and large regions in the US. An acre is 4,840 square yards, roughly the size of a football field, the traditional unit for land area in the US and UK. 1 mi² equals 640 ac, so converting between them is a matter of multiplying by that fixed factor — type any value into the converter below and both sides update instantly as you type.
Both units belong to area, measured here against area's base unit (m²) — every other area unit on this site converts through that same reference point, which is why the table below can also be read as a quick cross-check against nearby values.
Formula
ac = mi² × 640
mi² = ac × 0.0015625
Worked example: 5 mi² × 640 = 3,200 ac.
Conversion table
| Square Mile (mi²) | Acre (ac) |
|---|---|
| 1 mi² | 640 ac |
| 2 mi² | 1,280 ac |
| 3 mi² | 1,920 ac |
| 5 mi² | 3,200 ac |
| 10 mi² | 6,400 ac |
| 20 mi² | 12,800 ac |
| 25 mi² | 16,000 ac |
| 50 mi² | 32,000 ac |
| 100 mi² | 64,000 ac |
| 250 mi² | 160,000 ac |
| 500 mi² | 320,000 ac |
| 1,000 mi² | 640,000 ac |
Frequently asked
- How many Acres in a square mile?
- 1 mi² equals 640 ac.
- How do I convert Square Miles to Acres?
- Multiply the value in mi² by 640 to get ac. The converter above does this instantly as you type.
- Is the conversion exact?
- Yes — Square Mile and Acre are both defined by a fixed conversion factor to area's base unit (m²), so the result shown is exact to the precision displayed, not an approximation.