How this calculator works
The international mile is exactly 1,609.344 m, so a square mile is 1,609.344 squared in square metres, or 2,589,988.110336 m2. One square kilometre is 1,000,000 m2, which makes one square mile exactly 2.589988110336 km2. A square mile is also 640 acres, because an acre is 43,560 square feet and one square mile is 27,878,400 square feet. Square miles are still used for land area in the United States and the United Kingdom, while Canada uses square kilometres.
Formula
km2 = mi2 x 2.589988110336. mi2 = km2 / 2.589988110336. acres = mi2 x 640. ha = mi2 x 258.9988110336.
Worked example
1 mi2 = 2.58999 km2. 10 mi2 = 25.8999 km2. 5 mi2 = 12.9499 km2. 1 km2 = 0.386102 mi2. 1 mi2 = 640 acres = 259 ha. 100 mi2 = 258.999 km2.
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Frequently asked questions
Why is one square mile about 2.59 square kilometres?
One mile is 1.609344 km. Squaring that gives 2.589988110336. Area grows with the square of the length ratio, so the area factor is larger than the length factor.
How many acres are in a square mile?
A square mile is exactly 640 acres. The reason is that a square mile is 5,280 feet on each side, and an acre is 43,560 square feet, so 5,280 squared divided by 43,560 is 640.
How many square kilometres are in a hectare?
One square kilometre is 100 hectares, because a hectare is 10,000 m2 and a square kilometre is 1,000,000 m2. The table shows acres rather than hectares, but hectares appear in the equivalents table and are available in the output unit selector.
Is a square mile a mile on each side?
Yes, a square mile is a square with one mile sides. A land area of 500 square miles could have many other shapes with the same area.