How to convert square miles to acres
To convert a measurement in square miles to acres, multiply the value by 640. The conversion factor comes from the relationship between both units and the square meter.
For example, to convert 5 mi² to acres: 5 × 640 = 3,200 ac.
What is a square mile?
A square mile is an imperial and US customary unit of area equal to the area of a square one mile on each side, or 640 acres, about 2.59 square kilometers. The square mile is the traditional unit for large land areas in the US and UK. In the US Public Land Survey System, a 'section' is exactly one square mile, the building block of the township grid.
Common uses of square miles include: Areas of US and UK cities and counties; Land survey sections (640 acres); Geographic and census area reporting; Property and ranch land in imperial countries.
What is a acre?
An acre is an imperial and US customary unit of area equal to 43,560 square feet, or about 4,046.86 square meters (roughly 0.405 hectares). The acre originally meant the area a yoke of oxen could plow in a day, standardized as 1 chain by 1 furlong (66 by 660 feet). It remains the standard unit for land and farm area in the US and UK.
Common uses of acres include: Farmland and rural land size; Residential lot and property size in the US; Real estate and development parcels; Sports field and park area references.
Square Miles to acres worked examples
Here are some common values converted:
1 mi² = 640 ac 5 mi² = 3,200 ac 10 mi² = 6,400 ac 50 mi² = 32,000 ac 100 mi² = 64,000 ac
Frequently asked questions
How many acres are in one square mile?
One square mile (mi²) equals 640 acres (ac). Multiply any value in square miles by 640 to convert to acres.
How do I convert square miles to acres?
Multiply the value in square miles by 640. For example, 5 mi² × 640 = 3,200 ac.
How do I convert acres to square miles?
Multiply the value in acres by 0.0015625, or divide by 640. Use the swap button on the converter above to reverse the direction.
Is the square mile to acre conversion exact?
Yes. Area conversions derive from the exact 1959 international definitions of the meter, yard, and foot, so the factors are exact.
What is the formula for square miles to acres?
The formula is: ac = mi² × 640. This comes from the definition of both units relative to the square meter.