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1 km ≈ 1000000 mm.
Formula and calculation
mm = km × 1000000
Substituting 1 km gives approximately 1000000 mm. Definitions use the constants above; arithmetic uses browser floating point and displays at most 12 significant digits. The rounded table is not an instrument calibration or certified measurement.
Which units does this page use?
kilometers: one thousand metres.
millimeters: one thousandth of a metre.
When this direction is useful
Start here when your source record uses km for travel distances and route descriptions, but the receiving specification is expressed in mm for small components and manufacturing dimensions. Enter the original quantity rather than reusing a previously rounded result. If your source uses mm, use the reverse converter instead.
Conversion table
| kilometers (km) | millimeters (mm) |
|---|---|
| 0 | 0 |
| 1 | 1000000 |
| 5 | 5000000 |
| 10 | 10000000 |
| 100 | 100000000 |
Limits and interpretation
These are non-negative physical quantities; negative inputs are rejected. Converting a unit changes neither the measured object nor the original precision. Use a decimal dot; grouping commas are not accepted. No external rates, live data or account are involved.
Frequently asked questions
Can I convert the other way?
Yes. Convert millimeters to kilometers with the inverse equation. Rounding a result before converting it back can introduce a small difference.
Are these the same as every similarly named unit?
No. Check the two definitions above. International length, avoirdupois mass, US customary liquid measures and temperature readings are explicitly distinguished; an ambiguous label on a source document must be resolved first.
Where do the conversion definitions come from?
They use SI and defined customary conversion relationships. See the NIST Guide for the Use of SI. Output formatting is this tool's display policy, not extra measurement accuracy.