Square Miles to Acres Converter
Unit ConversionConvert square miles to acres. 1 square mile equals exactly 640 acres, with a conversion table, worked examples and the reverse conversion.
Acres
Equivalent area in acres
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SponsoredThis converter turns square miles into acres (sq mi to acres). Enter a value and the result updates as you type. 1 square mile equals exactly 640 acres.
US land surveys are built on this conversion: a section of land is nominally one square mile, and dividing it into quarters gives the 160-acre and 40-acre parcels still named in many deeds. It is also how a county, park or ranch area given in square miles turns into the acres used for land prices and farm plans.
The result is rounded to 2 decimal places, but the factor behind it never is, so long chains of conversions stay accurate. You can type decimals, thousands separators or fractions such as 2 1/2, and the conversion table below lists common values.
How Many Acres in a Square Mile
There are 640 acres in a square mile. A square mile is 5,280 feet on each side, 27,878,400 square feet, and dividing that by the 43,560 square feet in an acre gives exactly 640.
How to Convert Square Miles to Acres
To convert square miles to acres, multiply by 640. For example, 3 square miles equals exactly 1,920 acres.
To go from acres back to square miles, divide by 640. For example, 320 acres equals exactly 0.5 square miles.
Square Miles to Acres Conversion Table
Common values in square miles converted to acres, rounded to 2 decimal places.
| Square Miles | Acres |
|---|---|
| 0.0625 mi² | 40 ac |
| 0.25 mi² | 160 ac |
| 0.5 mi² | 320 ac |
| 1 mi² | 640 ac |
| 2 mi² | 1,280 ac |
| 5 mi² | 3,200 ac |
| 10 mi² | 6,400 ac |
| 25 mi² | 16,000 ac |
| 36 mi² | 23,040 ac |
| 100 mi² | 64,000 ac |
Sections, Quarter Sections and Townships
In the Public Land Survey System used across much of the US, Park County, Colorado describes a section as nominally one square mile, 640 acres, with 36 sections making a township. Real sections often differ from that ideal because of survey errors, terrain and the curvature of the Earth, so the acreage on a deed can be a little different from 640.
| Division | Square Miles | Acres |
|---|---|---|
| Township (36 sections) | 36 mi² | 23,040 ac |
| Section | 1 mi² | 640 ac |
| Half section | 0.5 mi² | 320 ac |
| Quarter section | 0.25 mi² | 160 ac |
| Quarter-quarter section | 0.0625 mi² | 40 ac |
Grazing and cropping plans start from these parcels, for example the Cattle per Acre Calculator for stocking rates and the Farm Profit Break-Even Calculator for returns per acre.
Frequently Asked Questions
How many acres is a tenth of a square mile?
0.1 square miles equals exactly 64 acres.
How many acres is 1.5 square miles?
1.5 square miles equals exactly 960 acres.
How many acres is 20 square miles?
20 square miles equals exactly 12,800 acres.
How many square miles is 1,000 acres?
1,000 acres equals exactly 1.5625 square miles.
What happens if I enter a negative number?
The result shows a dash. An area is a size, so it is never below zero; a negative value usually means a typing mistake, such as a stray minus sign.
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