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Square miles to acres

Multiply square miles by 640 to get acres.

1 mi² = 640 acNIST HB 44
mi²
6,400ac

10 mi² = 6,400 ac

How to convert square miles to acres

The acre is exactly 43 560 square feet (4046.8564224 m²). The square mile is exactly 2 589 988.110336 m² (1609.344 m squared).

Worked example — 10 mi²: 10 × 640 = 6,400 ac.

Square miles to acres table

Common conversions. The reverse table is on acres to square miles.
Square milesAcres
0.5 mi²320 ac
1 mi²640 ac
2 mi²1,280 ac
5 mi²3,200 ac
10 mi²6,400 ac
25 mi²16,000 ac
50 mi²32,000 ac
100 mi²64,000 ac
500 mi²320,000 ac

Reverse and related

About square miles and acres

Square mile (mi²)

1 mi² = 640 ac

Definition. Exactly 2 589 988.110336 m² (1609.344 m squared)

History and origin

The square mile is a square one mile on each side, built from the statute mile. It equals about 2.59 square kilometres, or 640 acres.

Current use

Square miles measure land, counties and regions in the United States and United Kingdom.

Source: NIST Handbook 44, Appendix C (area); 1959 yard-and-pound agreement

Acre (ac)

1 ac = 0.0015625 mi²

Definition. Exactly 43 560 square feet (4046.8564224 m²)

History and origin

The acre began as the area a yoke of oxen could plough in a day, later fixed as 43 560 square feet, or one furlong by one chain. It equals about 4047 square metres.

Current use

Acres are the customary measure for land, farm plots and larger properties in the United States and United Kingdom.

Source: NIST Handbook 44, Appendix C (area); 1959 yard-and-pound agreement

Where people use this

Square miles: land and county area. Acres: land and farm plots, US real estate. 1 square mile is exactly 640 acres.

How we know this is right
The factor is fixed by the standards that define the units, not chosen — so it is exact, not a measurement:
1 ac = 0.0015625 mi², so 1 mi² = 1 ÷ 0.0015625 = 640 ac.

Every value is carried to full double precision; the display is rounded.

Both units are defined in NIST Handbook 44, Appendix C (area); 1959 yard-and-pound agreement.

Questions people ask

How many acres in a square mile?

One square mile is exactly 640 acres.

How many acres is 2 square miles?

2 square miles is 1280 acres.

How many acres is half a square mile?

Half a square mile is 320 acres.

All square mile conversions