Unit Converter / Centimeters to Millimeters
Centimeters to Millimeters Converter
1 centimeter = 10 millimeters at 96 DPI, the CSS reference resolution. To convert, multiplycentimeters by 10: cm × 10 = mm. Change the DPI below for print and image work, where a pixel is whatever the output resolution says it is.
Centimeters to Millimeters table
Standard values at 96 DPI.
| Centimeters (cm) | Millimeters (mm) |
|---|---|
| 1 | 10 |
| 2 | 20 |
| 2.54 | 25.4 |
| 5 | 50 |
| 10 | 100 |
| 15 | 150 |
| 21 | 210 |
| 25 | 250 |
| 29.7 | 297 |
| 30 | 300 |
How the conversion works
The metric print unit outside the US: A4 paper is 21 by 29.7 centimeters. One centimeter is exactly 0.3937 inches. The fine metric unit: print tolerances, paper (A4 is 210 by 297 mm) and CSS print stylesheets use millimeters. Exactly 25.4 mm make an inch. The CSS specification anchors the whole system to the inch: at the reference resolution of 96 DPI, one inch is exactly 96 pixels, one point is 96/72 pixels, and the metric units follow from the inch being exactly 25.4 millimeters. Converting centimeters to millimeters therefore goes through that anchor: centimeters to pixels, then pixels to millimeters. For example,15 cm = 150 mm.
The DPI setting matters only when pixels meet the physical world. On screen, CSS pixels are defined by the 96 DPI reference and the conversion above is exact. In a 300 DPI print file or image, an inch holds 300 pixels instead, so the same measurement converts differently; set the resolution to match the file you are working with.