# Centimeters to Millimeters (cm to mm)

> Convert centimeters to millimeters: 1 cm = 10 mm. Exact conversion factor, formula, 22-row table and worked examples, with JSON API and MCP access.

- Page id: `cm-to-mm` · Quantity: Length (`length`, base unit m) · Tool: `convert_units`
- Canonical page: https://tttkmbb.com/conversion/cm-to-mm · This document: https://tttkmbb.com/conversion/cm-to-mm.md · JSON: https://tttkmbb.com/conversion/cm-to-mm.json (add `?value=` for a result)

## Formula

- `1 cm = 10 mm`
- `millimeters = centimeters × 10`
- Reverse: `centimeters = millimeters × 0.1`

The factor follows from the SI definitions of both units (NIST SP 811); values below are rounded to 6 significant figures, the API returns up to 12.

## Worked examples

- 5 cm = 50 mm
- 12.5 cm = 125 mm
- 100 cm = 1000 mm

## Conversion table

| Centimeters (cm) | Millimeters (mm) |
| --- | --- |
| 1 | 10 |
| 2 | 20 |
| 3 | 30 |
| 4 | 40 |
| 5 | 50 |
| 6 | 60 |
| 7 | 70 |
| 8 | 80 |
| 9 | 90 |
| 10 | 100 |
| 15 | 150 |
| 20 | 200 |
| 25 | 250 |
| 30 | 300 |
| 40 | 400 |
| 50 | 500 |
| 75 | 750 |
| 100 | 1000 |
| 200 | 2000 |
| 250 | 2500 |
| 500 | 5000 |
| 1000 | 10000 |

## API

- `GET https://tttkmbb.com/api/v1/convert?value=5&from_unit=cm&to_unit=mm` → unified JSON envelope with `result.values.result`, `formula`, `factor`, `sources`, `freshness`
- MCP: server `https://tttkmbb.com/mcp`, tool `convert_units` with `{"value":5,"from_unit":"cm","to_unit":"mm"}`
- All length units: https://tttkmbb.com/api/v1/units?quantity=length · full converter: [Length Converter](https://tttkmbb.com/conversion/length.md)
- Authentication: none. Freshness: `static` (fixed conversion factors).

## FAQ

**How many millimeters are in one centimeter?**

1 cm = 10 mm. The factor comes from the SI definitions of both units (NIST SP 811 / BIPM), so it is exact or correct to at least 10 significant figures.

**What is the formula to convert centimeters to millimeters?**

Multiply the value in centimeters by 10: millimeters = centimeters × 10. For example, 5 cm = 50 mm.

**How do I convert millimeters back to centimeters?**

Multiply by the inverse factor 0.1 (centimeters = millimeters × 0.1), or use the millimeters-to-centimeters page.

## Related conversions

- [Millimeters to centimeters](https://tttkmbb.com/conversion/mm-to-cm.md) (reverse)
- [Kilometers to Miles](https://tttkmbb.com/conversion/km-to-miles.md)
- [Miles to Kilometers](https://tttkmbb.com/conversion/miles-to-km.md)
- [Meters to Feet](https://tttkmbb.com/conversion/meters-to-feet.md)
- [Feet to Meters](https://tttkmbb.com/conversion/feet-to-meters.md)
- [Centimeters to Inches](https://tttkmbb.com/conversion/cm-to-inches.md)
- [Inches to Centimeters](https://tttkmbb.com/conversion/inches-to-cm.md)
- [Millimeters to Inches](https://tttkmbb.com/conversion/mm-to-inches.md)
- [Inches to Millimeters](https://tttkmbb.com/conversion/inches-to-mm.md)

## Data Sources

- NIST Special Publication 811 – Guide for the Use of the International System of Units (SI), Appendix B conversion factors — https://www.nist.gov/pml/special-publication-811 (standard, retrieved 2026-09-24)
- BIPM – The International System of Units (SI Brochure, 9th edition) — https://www.bipm.org/en/publications/si-brochure (standard, retrieved 2026-09-24)
- Wikipedia – Conversion of units — https://en.wikipedia.org/wiki/Conversion_of_units (reference, retrieved 2026-09-24)