Unit Converter / Millimeters to Inches
Millimeters to Inches Converter
1 millimeter = 0.0394 inches at 96 DPI, the CSS reference resolution. To convert, multiplymillimeters by 0.0394: mm × 0.0394 = in. Change the DPI below for print and image work, where a pixel is whatever the output resolution says it is.
Millimeters to Inches table
Standard values at 96 DPI.
| Millimeters (mm) | Inches (in) |
|---|---|
| 1 | 0.0394 |
| 5 | 0.1969 |
| 10 | 0.3937 |
| 25.4 | 1 |
| 50 | 1.9685 |
| 100 | 3.937 |
| 210 | 8.2677 |
| 254 | 10 |
| 297 | 11.6929 |
How the conversion works
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 US print unit: US Letter is 8.5 by 11 inches, and print layouts are still specced in inches across North America. 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 millimeters to inches therefore goes through that anchor: millimeters to pixels, then pixels to inches. For example,100 mm = 3.937 in.
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.