Square Miles to Square Kilometers
Convert square mile to square kilometer instantly — type a value and read the result, with the exact formula shown.
Example
1 mi² = 2.589988 km², 5 mi² = 12.94994 km², 10 mi² = 25.89988 km².
How it works
Square kilometer = Square mile × 2.589988. Every value is converted through a single square meter base unit using internationally defined conversion factors, so any from/to pair stays consistent.
Good to know
Converting square miles to square kilometers comes up most often when you're comparing land areas across borders: a US national park, county, or metro region is usually measured in square miles, while the rest of the world reports the same area in square kilometers. It also shows up in geography homework, real-estate and ranch listings, wildfire and flood coverage maps, and any time you read a US news story and want the figure in metric terms you can picture.
The two units sit on opposite sides of the metric/imperial divide. The square mile is an imperial and US customary unit built on the statute mile (5,280 feet), so one square mile is 640 acres. The square kilometer is the SI-derived metric unit, simply a square that is 1,000 metres on each side, equal to 100 hectares. Because a mile is longer than a kilometer, a square mile covers more ground than a square kilometer — by a factor of roughly two and a half.
For mental math, treat the factor as "about 2.6": multiply square miles by 2.6 to get square kilometers, and divide by 2.6 (or multiply by ~0.39) to go back. A handy anchor is that 100 square miles is almost exactly 259 square kilometers. The exact factor is 2.589988 km² per mi².
- Mistake to avoid: never convert area by the linear mile-to-kilometer factor (1.609). Area scales with the square, so the correct factor is 1.609² ≈ 2.59 — using 1.609 understates the answer by about 38%.
Frequently asked questions
How do you convert square mile to square kilometer?
Multiply the number of square miles by 2.589988 to get square kilometers. For example, 1 mi² = 2.589988 km².
What is 1 square mile in square kilometers?
1 square mile equals 2.589988 square kilometers (1 mi² = 2.589988 km²).
How many square miles are in 1 square kilometer?
There are 0.3861022 square miles in 1 square kilometer.
Is this converter free and private?
Yes. It runs entirely in your browser, so your inputs never leave your device, there is no sign-up, and it works offline once loaded.
Are the conversions exact?
Conversions use internationally defined factors and are exact where the definitions are exact (for example, 1 inch = 2.54 cm). Displayed results are rounded for readability.
People also ask
How many square kilometers are in a square mile?
There are 2.589988 square kilometers in one square mile. For rough estimates you can round to 2.59 or even 2.6.
How do I convert square kilometers back to square miles?
Divide square kilometers by 2.589988, or multiply by 0.3861022. For example, 10 km² equals about 3.861 square miles.
How many square kilometers is 100 square miles?
100 square miles equals 258.9988 square kilometers, which rounds neatly to about 259 km².
How many acres are in a square mile, and how does that relate to square kilometers?
One square mile is exactly 640 acres, and it equals 2.589988 square kilometers. Since a square kilometer is 100 hectares, one square mile is about 258.999 hectares.
Why isn't the conversion factor just 1.609 like miles to kilometers?
Because area is two-dimensional, you square the linear factor: 1.609344² = 2.589988. Using 1.609 directly would give the wrong area, off by about 38 percent.
How big is a square mile compared to a square kilometer?
A square mile is larger — about 2.59 square kilometers. Conversely, a square kilometer is only about 0.386 of a square mile.
What is 5 square miles in square kilometers?
5 square miles equals 12.94994 square kilometers (5 × 2.589988). Rounded, that's roughly 12.95 km².
Is the square mile to square kilometer conversion exact?
Yes, the factor 2.589988 km² per mi² is exact because the international mile is defined exactly as 1,609.344 metres. Displayed results are just rounded for readability.
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