Square Mile to Acre Converter
Convert Square Mile (mi²) to Acre (ac) instantly. 1 mi² = 640 ac.
Area Converter
20 units available
1 mi² = 640 ac
Formula:
ac = mi² × 640With your value: 1 mi² = 640 ac
How big is that?
Everyday references on a logarithmic scale, all expressed in square mile so you can sanity-check the result.
Other Square Mile to Acre conversions
Square Mile to Acre Conversion Table
| Square Mile (mi²) | Acre (ac) |
|---|---|
| 0.5 | 320 |
| 1 | 640 |
| 2 | 1,280 |
| 5 | 3,200 |
| 10 | 6,400 |
| 15 | 9,600 |
| 20 | 12,800 |
| 25 | 16,000 |
| 50 | 32,000 |
| 100 | 64,000 |
| 250 | 160,000 |
| 500 | 320,000 |
| 1000 | 640,000 |
Acre to Square Mile Conversion Table
| Acre (ac) | Square Mile (mi²) |
|---|---|
| 0.5 | 0.000781 |
| 1 | 0.001563 |
| 2 | 0.003125 |
| 5 | 0.007813 |
| 10 | 0.015625 |
| 15 | 0.023438 |
| 20 | 0.03125 |
| 25 | 0.039063 |
| 50 | 0.078125 |
| 100 | 0.15625 |
| 250 | 0.390625 |
| 500 | 0.78125 |
| 1000 | 1.5625 |
Where these values come from
Every factor on this page is traced to the document that defines it. See the full provenance dataset or our methodology.
Square Mile (mi²)
Area
Derived from the square metre via the length definitions above.
Source: NIST Special Publication 811, Guide for the Use of the International System of Units
National Institute of Standards and Technology (US) · Reviewed 2026-07-01
Acre (ac)
Area
Derived from the square metre via the length definitions above.
Source: NIST Special Publication 811, Guide for the Use of the International System of Units
National Institute of Standards and Technology (US) · Reviewed 2026-07-01
How to Convert Square Mile to Acre
To convert from Square Mile (mi²) to Acre (ac), multiply the value by 640.
Formula: ac = mi² × 640
Reverse: mi² = ac × 0.0015625
Step-by-Step Example
- Start with your value in Square Mile. For example: 5 mi²
- Multiply by the conversion factor: 5 x 640
- The result is: 3,200 ac
About Square Mile
The square mile equals 640 acres or about 2.59 square kilometres, and is the standard unit for US county, city and land-survey areas.
Common uses: census areas, land surveys, geography.
About Acre
The acre is a unit of land area equal to 43,560 square feet or about 4,047 square meters. It is used primarily in the US, UK, and former British colonies.
Fun Fact: An acre was originally defined as the amount of land a yoke of oxen could plow in one day.
Common uses: land measurement, agriculture, real estate.
Frequently Asked Questions
How many Acre are in 1 Square Mile?
There are exactly 640 Acre in 1 Square Mile. This means the conversion factor from Square Mile to Acre is 640.
What is the formula to convert Square Mile to Acre?
The formula to convert Square Mile to Acre is: ac = mi² × 640. For example, to convert 10 Square Mile to Acre, you would multiply 10 by 640.
What is a Square Mile?
The square mile equals 640 acres or about 2.59 square kilometres, and is the standard unit for US county, city and land-survey areas.
What is a Acre?
The acre is a unit of land area equal to 43,560 square feet or about 4,047 square meters. It is used primarily in the US, UK, and former British colonies.
What are the common uses of Square Mile?
The Square Mile is commonly used in census areas, land surveys, geography.
Related Area Conversions
Cite this page
UnitConvertLab. (2026). Square Mile to Acre converter. UnitConvertLab. Retrieved from https://unitconvertlab.com/convert/sqmile-to-acre