Acres to Square Miles Converter

About the ac to mi² calculation

One acre is exactly 0.0015625 square miles, so converting between them is a single multiplication. Enter any value above and the result updates as you type. The standard land unit in the US and UK — originally the area one ox team could plough in a day. Used for land and territory area in the US and UK. One square mile is exactly 640 acres.

Formula

mi² = ac × 0.0015625

1 ac = 0.0015625 mi²
1 mi² = 640 ac

Worked example

To convert 1 ac, multiply by 0.0015625: 1 × 0.0015625 = 0.0015625 mi².

Frequently asked questions

How many square miles are in a acre?

There are 0.0015625 square miles in one acre. To convert any amount, multiply the number of acres by 0.0015625.

How do I convert square miles back to acres?

Divide instead of multiplying, or equivalently multiply by 640. One square mile is 640 acres.

Is this conversion exact?

Yes. Since the international agreement of 1959, the relationship between acres and square miles is defined exactly rather than measured, so the only rounding here is in how many decimal places we show.

Where is each of these units used?

Acres: the standard land unit in the US and UK — originally the area one ox team could plough in a day. Square Miles: used for land and territory area in the US and UK. One square mile is exactly 640 acres.

Sources

• NIST Special Publication 811 — Guide for the Use of the International System of Units