About the ft² to mi² calculation
One square foot is exactly 3.5870e-8 square miles, so converting between them is a single multiplication. Enter any value above and the result updates as you type. How property floor area is quoted in the US, UK and India. Used for land and territory area in the US and UK. One square mile is exactly 640 acres.
Formula
mi² = ft² × 3.5870e-8
1 ft² = 3.5870e-8 mi²
1 mi² = 27,878,400 ft²Worked example
To convert 1,000 ft², multiply by 3.5870e-8: 1,000 × 3.5870e-8 = 0.00003587 mi².
Frequently asked questions
How many square miles are in a square foot?
There are 3.5870e-8 square miles in one square foot. To convert any amount, multiply the number of square feet by 3.5870e-8.
How do I convert square miles back to square feet?
Divide instead of multiplying, or equivalently multiply by 27,878,400. One square mile is 27,878,400 square feet.
Is this conversion exact?
Yes. Since the international agreement of 1959, the relationship between square feet 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?
Square Feet: how property floor area is quoted in the US, UK and India. 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