How to Convert Square kilometres to Square millimetres (km² to mm²)
Area conversions are everyday maths in Singapore property: HDB flats are listed in square metres while condo listings and PSF prices use square feet. This guide shows how to convert square kilometres into square millimetres by hand, with examples and a quick-reference table.
The conversion
To convert square kilometres to square millimetres, multiply the value by 1.000000e+12. To go the other way, divide by the same number (or multiply by 1.000000e-12). For a quick estimate, multiply by about 1,000,000,000,000.
Square millimetres = square kilometres × 1.000000e+12
Worked examples
- 3 km² = 3.000000e+12 mm²
- 12.5 km² = 1.250000e+13 mm²
- 75 km² = 7.500000e+13 mm²
Square kilometres to Square millimetres table
| Square kilometres | Square millimetres |
|---|---|
| 1 km² | 1.000000e+12 mm² |
| 2 km² | 2.000000e+12 mm² |
| 5 km² | 5.000000e+12 mm² |
| 10 km² | 1.000000e+13 mm² |
| 20 km² | 2.000000e+13 mm² |
| 25 km² | 2.500000e+13 mm² |
| 50 km² | 5.000000e+13 mm² |
| 100 km² | 1.000000e+14 mm² |
| 250 km² | 2.500000e+14 mm² |
| 500 km² | 5.000000e+14 mm² |
| 1,000 km² | 1.000000e+15 mm² |
Common questions
Is km² to mm² exact?
The factors used here are the internationally defined values where they exist; results are rounded for display only.
How do I convert back?
Use the Square millimetres to Square kilometres converter.
Mistakes to avoid
Multiplying when you should divide
Converting to a smaller unit gives a bigger number, and converting to a larger unit gives a smaller one. If your answer moves the wrong way, you have inverted the factor.
Mixing similar-sounding units
US and imperial gallons, pints and tons are different sizes, and decimal kilobytes differ from binary kibibytes.
Dropping the units
A bare number without a unit is easy to misread later. Always write the unit with the result.
Background
For everyday use, three or four significant figures are usually enough. Engineering, science and trade documents may need more, and rounding should happen only at the end of a calculation.
Writing the units next to every number while you work is the simplest way to avoid mistakes. If the units do not cancel to leave the one you want, the calculation is set up wrongly.
Many conversion factors are exact by definition. The inch has been defined as exactly 2.54 centimetres since 1959, and the pound as exactly 0.45359237 kilograms, so conversions involving them can be as precise as you need.
For any value, use the Square kilometres to Square millimetres Converter or browse all area converters.
Run your own numbers: Square kilometres to Square millimetres Converter