Millimetres to Kilometres converter
Convert Millimetres (mm) to Kilometres (km). Calculate a value, check the formula and compare common measurements.
Result for the values shown.
Calculations run in your browser.
What to enter
| Input | Meaning and units |
|---|---|
| Value | Enter value using the definition in the method and example. |
| From | Select the unit or currency in which the entered number is currently expressed. |
| To | Select the unit or currency you need for the answer. |
Understanding your result
The converted value describes the same length quantity in the selected target unit. Display rounding does not add precision to the original measurement.
Common mistakes
- Confusing the source and target units, or overlooking a prefix or case-sensitive symbol.
Check your calculation
- Convert to the target unit and then reverse the direction. Within display rounding, you should recover the original value.
Read the length measurement guide · Calculation checks, sources and review limits
How do I convert millimetres to kilometres?
Enter the value in millimetres to find the same length quantity in kilometres. The number changes to match the unit; the underlying quantity stays the same. Check the definitions below when a unit has more than one convention.
Common uses
- Compare distances or dimensions expressed in different units.
- Translate measurements before using them in a calculation.
How it works
For the displayed direction, 1 mm equals 0.000001 km. The engine converts through the shared length base quantity. Distances use international definitions. Light-years use a 365.25-day Julian year. The parsec follows the IAU angular definition and uses finite numerical precision. The multiplier is derived from the two centralized unit factors. Keep full precision until the final result; displayed answers use up to 12 significant digits.
Worked example
10 mm converts to 0.00001 km. For the reverse direction, swap the units and enter 0.00001 km; the result is approximately 10 mm.
FAQ
How do I convert mm to km?
km = mm × 0.000001
Which definition is used?
Distances use international definitions. Light-years use a 365.25-day Julian year. The parsec follows the IAU angular definition and uses finite numerical precision.
Common values
Use “Swap units” above for the reverse conversion. Values below are rounded to six significant digits.
| Millimetres | Kilometres |
|---|---|
| 1 | 0.000001 |
| 5 | 0.000005 |
| 10 | 0.00001 |
| 20 | 0.00002 |
| 30 | 0.00003 |
| 50 | 0.00005 |
| 100 | 0.0001 |