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Area
Square miles to Acres
Convert square miles (mi²) to acres (ac). Type a value below to see the result update instantly. Reference table and formula included.
Calculator
1 mi² = 640 ac
Square miles to Acres Conversion Table
Common values, ready to copy:
| square miles | acres |
|---|---|
| 1 mi² | 640 ac |
| 2 mi² | 1280 ac |
| 5 mi² | 3200 ac |
| 10 mi² | 6399.99 ac |
| 25 mi² | 15999.99 ac |
| 50 mi² | 31999.97 ac |
| 100 mi² | 63999.94 ac |
| 1,000 mi² | 639999.43 ac |
Formula
acres = square miles × 6.39999434e+2
Area conversions are derived from length: 1 ft² = (0.3048 m)² = 0.092903 m². 1 acre = 4,046.86 m². 1 hectare = 10,000 m² exactly.
About Square miles and Acres
Square miles (mi²): One mile squared, or 2.59 km²; the standard US unit for large land areas. Common uses: City and county area, state and national park sizes, watersheds, and large geographic features in the US.
Acres (ac): An old English unit, originally the area a yoke of oxen could plow in a day; standardized at exactly 4,046.86 m² (43,560 sq ft). Common uses: Land area in the US, UK, and most former British colonies — farm sizes, residential lots, and ranch acreage.
How the conversion works
Area conversions are derived from length: 1 ft² = (0.3048 m)² = 0.092903 m². 1 acre = 4,046.86 m². 1 hectare = 10,000 m² exactly.
The exact relationship is acres = square miles × 6.39999434e+2, which the calculator at the top of this page applies in both directions. Type into either field and the other updates immediately.
When this conversion matters
Converting between square miles and acres comes up wherever area measurements move between systems — from one country's conventions to another's, from a scientific reference to a practical specification, or from one industry's working unit to another's. The calculator and reference table above cover the everyday range; for unusual values you can type any number into either field.