Square Miles to Acres Conversion (sq mi to ac)

Square Miles to Acres Converter

Enter the area in square miles below to get the value converted to acres.

Results in Acres:

1 sq mi = 640 ac

How to Convert Square Miles to Acres

To convert a measurement in square miles to a measurement in acres, multiply the area by the following conversion ratio: 640 acres/square mile.

Since one square mile is equal to 640 acres, you can use this simple formula to convert:

acres = square miles × 640

The area in acres is equal to the area in square miles multiplied by 640.

For example, here's how to convert 5 square miles to acres using the formula above.

acres = (5 sq mi × 640) = 3,200 ac

conversion scale showing square miles and equivalent acres area values

How Many Acres Are in a Square Mile?

There are 640 acres in a square mile, which is why we use this value in the formula above.

1 sq mi = 640 ac

Square miles and acres are both units used to measure area. Keep reading to learn more about each unit of measure.

What is a Square Mile?

One square mile is equal to the area of a square with sides that are each 1 mile long. One square mile is roughly equal to 2.59 square kilometers or 640 acres.

The square mile is a US customary and imperial unit of area. Square miles can be abbreviated as sq mi, and are also sometimes abbreviated as mi². For example, 1 square mile can be written as 1 sq mi or 1 mi².

Learn more about square miles.

What is an Acre?

One acre is defined as the area equal to a space that is one chain (66 ft) by one furlong (660 ft), or 10 square chains.^[1] That's equal to 43,560 square feet or 1/640 of a square mile for those unfamiliar with those units of measure.

illustration showing the size of an acre is a parcel of land that is 66 feet by 660 feet.

The acre is a US customary and imperial unit of area. Acres can be abbreviated as ac; for example, 1 acre can be written as 1 ac.

You can use an acreage calculator to measure the area of a plot of land in acres by locating the boundaries on a map.

Learn more about acres.

Square Mile to Acre Conversion Table

Table showing various square mile measurements converted to acres.
Square Miles	Acres
1 sq mi	640 ac
2 sq mi	1,280 ac
3 sq mi	1,920 ac
4 sq mi	2,560 ac
5 sq mi	3,200 ac
6 sq mi	3,840 ac
7 sq mi	4,480 ac
8 sq mi	5,120 ac
9 sq mi	5,760 ac
10 sq mi	6,400 ac
11 sq mi	7,040 ac
12 sq mi	7,680 ac
13 sq mi	8,320 ac
14 sq mi	8,960 ac
15 sq mi	9,600 ac
16 sq mi	10,240 ac
17 sq mi	10,880 ac
18 sq mi	11,520 ac
19 sq mi	12,160 ac
20 sq mi	12,800 ac
21 sq mi	13,440 ac
22 sq mi	14,080 ac
23 sq mi	14,720 ac
24 sq mi	15,360 ac
25 sq mi	16,000 ac
26 sq mi	16,640 ac
27 sq mi	17,280 ac
28 sq mi	17,920 ac
29 sq mi	18,560 ac
30 sq mi	19,200 ac
31 sq mi	19,840 ac
32 sq mi	20,480 ac
33 sq mi	21,120 ac
34 sq mi	21,760 ac
35 sq mi	22,400 ac
36 sq mi	23,040 ac
37 sq mi	23,680 ac
38 sq mi	24,320 ac
39 sq mi	24,960 ac
40 sq mi	25,600 ac

Table showing various square mile measurements converted to acres.

Square Miles

Acres

1 sq mi

640 ac

2 sq mi

1,280 ac

3 sq mi

1,920 ac

4 sq mi

2,560 ac

5 sq mi

3,200 ac

6 sq mi

3,840 ac

7 sq mi

4,480 ac

8 sq mi

5,120 ac

9 sq mi

5,760 ac

10 sq mi

6,400 ac

11 sq mi

7,040 ac

12 sq mi

7,680 ac

13 sq mi

8,320 ac

14 sq mi

8,960 ac

15 sq mi

9,600 ac

16 sq mi

10,240 ac

17 sq mi

10,880 ac

18 sq mi

11,520 ac

19 sq mi

12,160 ac

20 sq mi

12,800 ac

21 sq mi

13,440 ac

22 sq mi

14,080 ac

23 sq mi

14,720 ac

24 sq mi

15,360 ac

25 sq mi

16,000 ac

26 sq mi

16,640 ac

27 sq mi

17,280 ac

28 sq mi

17,920 ac

29 sq mi

18,560 ac

30 sq mi

19,200 ac

31 sq mi

19,840 ac

32 sq mi

20,480 ac

33 sq mi

21,120 ac

34 sq mi

21,760 ac

35 sq mi

22,400 ac

36 sq mi

23,040 ac

37 sq mi

23,680 ac

38 sq mi

24,320 ac

39 sq mi

24,960 ac

40 sq mi

25,600 ac

References

National Institute of Standards and Technology, Specifications, Tolerances, and Other Technical Requirements for Weighing and Measuring Devices, Handbook 44 - 2019 Edition, https://nvlpubs.nist.gov/nistpubs/hb/2019/NIST.HB.44-2019.pdf