Convert Square Mile to Square Kilometer
Convert square miles to square kilometers instantly. 1 square mile = 2.5899881103 square kilometer — use the live calculator, the exact formula, a conversion table and worked examples. Also check the Square Kilometer to Square Mile converter for the reverse conversion.
Units explained
Square Mile
A square mile is an imperial unit of area equal to exactly 2,589,988.110336 m². It is used for measuring large land areas in the United States and the United Kingdom.
Derived by squaring the statute mile (5,280 feet). The mile was standardized via the 1959 International Yard and Pound Agreement.
Square miles are used for US and UK regional geography (county areas, lake sizes, large parks), national statistics, and military range descriptions. 1 mi² = 640 acres = 2.589988 km².
Mile dates to Roman antiquity; modern exact value standardized in 1959.
Square Kilometer
A square kilometer is a metric unit of area equal to 1,000,000 m² (one million square meters), or 100 hectares. It is used for measuring large land areas, regional geography, and country-scale statistics.
Derived by squaring the kilometer (1000 m). The kilo- prefix comes from the Greek 'chilioi' (thousand).
Square kilometers express the area of cities, districts, lakes, forests, and entire countries. India's total area is approximately 3,287,263 km². 1 km² equals 100 hectares or about 247.105 acres.
Kilometer has been part of the metric system since 1795.
Square Mile to Square Kilometer conversion formula
The relationship between square miles and square kilometers:
To convert square miles to square kilometers, multiply the value in square miles by 2.5899881103. To reverse, multiply square kilometers by 0.3861021585.
How to use this converter
Type a value into the calculator. The result in square kilometers updates as you type. Tap a quick value, copy the result with one click, or use the swap arrow to jump straight to the Square Kilometer to Square Mile converter for the reverse direction.
Step-by-step: convert square miles to square kilometers
- Write down the value in square miles (mi²).
- Multiply that value by the factor 2.5899881103.
- The product is the equivalent value in square kilometers (km²).
- To reverse, multiply the square kilometer value by 0.3861021585.
Worked examples
Example 1 — Convert 1 mi² to km²:
1 × 2.5899881103 = 2.5899881103 km²
Example 2 — Convert 100 mi² to km²:
100 × 2.5899881103 = 258.9988110336 km²
Square Mile to Square Kilometer conversion table
Standard reference values for converting square miles to square kilometers:
| Square Mile [mi²] | Square Kilometer [km²] |
|---|---|
| 0.01 | 0.0258998811 |
| 0.1 | 0.258998811 |
| 1 | 2.5899881103 |
| 2 | 5.1799762207 |
| 3 | 7.769964331 |
| 4 | 10.3599524413 |
| 5 | 12.9499405517 |
| 10 | 25.8998811034 |
| 20 | 51.7997622067 |
| 30 | 77.6996433101 |
| 40 | 103.5995244134 |
| 50 | 129.4994055168 |
| 100 | 258.9988110336 |
| 500 | 1294.994055168 |
| 1000 | 2589.988110336 |
Frequently asked questions
How many square kilometers is 1 square mile?
How do I convert square miles to square kilometers?
How do I convert square kilometers back to square miles?
How many square kilometers is 100 square miles?
Popular area unit conversions
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Metric / SI (5 units)
Imperial / US Customary (14 units)
Sources & references
Conversion factor (1 mi² = 2.5899881103 km²) verified against the following authoritative sources:
- BIPM — The International System of Units (SI Brochure 9th ed.)
Official BIPM publication defining the seven SI base units (including the meter) and the rules for their use. The global authority on units of measurement.
- NIST — Guide to the SI
US National Institute of Standards and Technology reference covering the SI base and derived units with definitions and usage rules for US technical practice.
- NIST Special Publication 811 — Guide for the Use of the International System of Units
Detailed NIST guide covering exact conversion factors between SI and US customary units along with formatting and rounding conventions.
- NIST — Refinement of values for the yard and pound (Federal Register 1959)
The treaty (signed by US
- International Hydrographic Organization — Resolution on the Nautical Mile
International authority that standardised the nautical mile at exactly 1852 m in 1929 — the value adopted worldwide for sea and air navigation.