Square Mile to Square Kilometre
Free instant square mile to square kilometre converter. 1 mi² = 2.58999 km².
Common Square Mile to Square Kilometre values
| Square Mile (mi²) | Square Kilometre (km²) |
|---|---|
| 1 | 2.58999 |
| 5 | 12.9499 |
| 10 | 25.8999 |
| 25 | 64.7497 |
| 50 | 129.499 |
| 100 | 258.999 |
| 500 | 1294.99 |
| 1000 | 2589.99 |
How does Square Mile to Square Kilometre conversion work?
Type a value in the Square Mile (mi²) field and the equivalent in Square Kilometre (km²) appears instantly to the right. The math uses the exact formula shown above — no rounding errors, no approximations beyond standard floating-point precision. Use the swap button to flip the units and see the inverse conversion.
Square Mile. A square one mile on each side. About 2.59 square kilometres or 640 acres.
Square Kilometre. A square one kilometre on each side. Equal to 100 hectares or about 247 acres.
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🎯 Accurate conversions
Conversion factors come from the official standard (NIST, BIPM, ISO definitions where applicable). Values are precise to standard floating-point limits.
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How it works — the formula
Area scales as length squared.
For any length scale s (metres per unit), area scale = s².
1 ft² = 0.3048² m² = 0.09290304 m² exactly
1 acre = 4,046.8564224 m² exactly (= 1 chain × 1 furlong)Area is a derived unit — the square of length — so any area conversion factor is the square of the corresponding length factor. The acre (4,046.8564224 m²) and hectare (10,000 m² exactly) are both standardized; one acre is also exactly 43,560 ft². Square metre is the SI derived unit.
Worked examples
- Inputs:
- 1,500 ft² = ? m²
- Output:
- 1,500 × 0.09290304 ≈ 139.355 m²
- Inputs:
- 5 acres = ? ha
- Output:
- 5 × 4,046.8564224 / 10,000 ≈ 2.0234 ha
- Inputs:
- (1 ft)² in m²
- Output:
- (0.3048 m)² = 0.0929 m² — squaring confirms the area scale
Limitations
- Land-survey areas may use "US survey foot" rather than international foot — the difference is ~4 ppm, deprecated as of 2023.
- Surface area on a curved manifold (sphere, ellipsoid) requires intrinsic geometry, not the flat conversion factor.
- Floor-area definitions (gross vs net vs rentable) are governed by BOMA / IPMS standards, not unit conversion.
- Pixel-area (digital images) is not a physical area unit — px² depend on display DPI.
Area conversions are exact rational arithmetic for SI ↔ US-customary; trailing-digit differences come from binary floating-point only.