Mm to cm converter
Convert millimeters to centimeters instantly. The relationship is simple: 1 cm = 10 mm.
Converting mm to cm
Both millimeters and centimeters are metric units, so the conversion is a simple decimal shift: divide mm by 10 to get cm. Despite being trivial math, this is one of the most searched unit conversions because people want instant confirmation — especially when working with precision measurements, paper sizes, or hardware specs.
The relationship is exact by definition: 1 centimeter = 10 millimeters. There's no approximation, no historical agreement to reference — it's a direct consequence of the metric system's decimal structure. A millimeter is one-thousandth of a meter; a centimeter is one-hundredth.
Common small measurements
Everyday objects measured in mm and their cm equivalents:
| mm | cm | Typical context |
|---|---|---|
| 1 mm | 0.1 cm | Pencil lead |
| 5 mm | 0.5 cm | Phone thickness |
| 10 mm | 1 cm | Coin diameter |
| 25 mm | 2.5 cm | USB-C port width |
| 50 mm | 5 cm | Credit card length |
| 100 mm | 10 cm | Smartphone screen |
| 200 mm | 20 cm | Tablet screen |
| 500 mm | 50 cm | Laptop keyboard width |
Paper and stationery sizes
Standard paper sizes are defined in mm. Here they are in cm:
| Size (mm) | Size (cm) | Format |
|---|---|---|
| 210 × 297 mm | 21.0 × 29.7 cm | A4 |
| 148 × 210 mm | 14.8 × 21.0 cm | A5 |
| 85 × 55 mm | 8.5 × 5.5 cm | Business card |
Frequently asked
Use the full length converter to convert between cm, meters, feet, inches, yards, miles, and more — all 14 units in one place.