Acres to Square Miles
Convert acres to square miles instantly. 1 ac = 0.0015625 mi². Includes the exact factor, a conversion table of common values and the definition of both units.
How to convert acres to square miles
To convert acres to square miles, divide by 640 (multiply by 0.0015625). The relationship is fixed, so the same factor works for any quantity — there is nothing to look up and nothing that changes with temperature, location or context.
mi² = ac × 0.0015625
Acres to Square Miles conversion table
The values people look up most often, rounded for reading. Use the calculator above for anything in between.
| Acres | Square Miles |
|---|---|
| 1 ac | 0.001563 mi² |
| 2 ac | 0.003125 mi² |
| 3 ac | 0.004688 mi² |
| 5 ac | 0.007812 mi² |
| 10 ac | 0.015625 mi² |
| 20 ac | 0.03125 mi² |
| 25 ac | 0.039062 mi² |
| 50 ac | 0.078125 mi² |
| 100 ac | 0.15625 mi² |
| 500 ac | 0.78125 mi² |
| 1,000 ac | 1.5625 mi² |
What is a acre?
43,560 square feet — historically the area one ox team could plough in a day.
What is a square mile?
640 acres. Used for counties, states and weather-warning areas.
The formula
mi² = ac × 0.0015625
Every result on this page comes from this formula. Nothing is rounded until the final display, so figures match a spreadsheet to the cent.
How to use the Acres to Square Miles
- Type the number of acres you want to convert.
- Read the result in square miles straight away — there is no button to press.
- Check the table below for the values that come up most often, or reverse the conversion with the linked square miles to acres page.
Acres to Square Miles — frequently asked questions
How many square miles are in a acre?
One acre equals 0.0015625 mi². mi² = ac × 0.0015625
What is the formula to convert acres to square miles?
The formula is mi² = ac × 0.0015625. It is an exact definition rather than an approximation, so the conversion never drifts no matter how large the number.
How do I convert square miles back to acres?
Divide instead of multiplying: one square mile is 640 ac. The reverse converter is linked in the related tools list.
Is this conversion exact?
Yes. Both units are defined against the same base unit by international agreement, so the factor is exact — any rounding you see is only in the display, which you can widen by entering more decimal places.
Is this acres to square miles free to use?
Yes. Every calculator on the site is free, needs no sign-up, and runs entirely in your browser, so your figures never leave your device.
What people search for
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About this calculator
Written and reviewed by The Samsung Calculator editorial team. Every calculator is written against a published formula, reviewed against at least one independent reference implementation, and dated when it changes.
Last reviewed August 15, 2026 · Calculation runs client-side · No data collected · Report an error