Length and Area
kmtomm
Convert kilometres (km) to millimetres (mm).
Factor1 km = 1000000 mm
Converter
km
Accepts numbers or expressions, e.g. 150 + 14.7
Result
mm
Rendered to 6 significant figures.
Formula
Formula
mm = km × 1000000
Multiply any value in kilometres by 1000000 to obtain the value in millimetres.
Worked example
Convert 1 km to mm.
- 01Start with 1 km.
- 02Multiply by the conversion factor: 1 × 1000000 = 1.00000e+6 mm.
Result1 km = 1.00000e+6 mm
Conversion table
| km | mm |
|---|---|
| 1 | 1.0000e+6 |
| 2 | 2.0000e+6 |
| 5 | 5.0000e+6 |
| 10 | 1e+7 |
| 20 | 2e+7 |
| 50 | 5e+7 |
| 100 | 1e+8 |
| 200 | 2e+8 |
| 500 | 5e+8 |
| 1000 | 1e+9 |
Reference values rounded to 5 significant figures for display.
FAQ
What is the conversion factor from km to mm?
1 km equals 1000000 mm. To convert, multiply the value in kilometres by 1000000.
How do I convert 1 km to mm?
1 km = 1.00000e+6 mm. For any value, multiply by 1000000.
How do I convert mm back to km?
Divide by the same factor — or equivalently, multiply by 1e-6. So 1 mm = 1e-6 km.
When would I need to convert kilometre to millimetre?
Length conversions appear in piping, layout, and mechanical drawings — particularly when reconciling imperial fittings or instrument lengths with metric plant drawings.
Is the conversion exact?
Yes. Both km and mm are defined by exact SI relationships, so the displayed factor is exact (any rounding shown is only for display).