Convert px to mm
1px = 0.264583mm. Both are absolute CSS units, so this ratio is fixed — the root font size does not affect it.
Guide & FAQFormula · PX to MM conversion table · About px · About mm · Which unit should you use? · Frequently asked questions
Formula
mm = px × 0.264583
px = mm × 3.7795Both units are absolute in CSS, so this ratio never changes regardless of font size or user settings.
PX to MM conversion table
| px | mm |
|---|---|
| 1px | 0.264583mm |
| 10px | 2.6458mm |
| 50px | 13.2292mm |
| 100px | 26.4583mm |
| 150px | 39.6875mm |
| 200px | 52.9167mm |
| 250px | 66.1458mm |
| 300px | 79.375mm |
| 400px | 105.83mm |
| 500px | 132.29mm |
| 600px | 158.75mm |
| 800px | 211.67mm |
| 1000px | 264.58mm |
| 1080px | 285.75mm |
| 1200px | 317.5mm |
| 1500px | 396.87mm |
| 1920px | 508mm |
About px
The CSS pixel is the reference unit of the web. It is not a physical device pixel — it is an angular measure standardised at 1/96th of an inch, which the browser scales for device pixel ratio and zoom.
About mm
One millimetre is about 3.78 CSS pixels. Like centimetres it is a print unit that CSS accepts everywhere.
Which unit should you use?
| Property | Recommended unit | Why |
|---|---|---|
| Font size | rem | Scales with the user's browser font-size preference, which px ignores — an accessibility requirement. |
| Padding and margin | rem or em | rem for a consistent global rhythm; em when the spacing should track the component's own text size. |
| Borders and hairlines | px | You almost always want exactly one crisp pixel, not a value that scales. |
| Media query breakpoints | em | Historically the most reliable across browsers when the user zooms. |
| Print stylesheets | pt, cm, mm | These map to real physical measurements on paper. |
Frequently asked questions
What is 16px in mm?
16px equals 4.2333mm, and that does not change with the font size because both units are absolute.
How do I convert px to mm?
Multiply the px value by 0.264583. Going the other way, multiply the mm value by 3.7795.
Does browser zoom change the result?
No. Both units are absolute in CSS and keep the same ratio at any zoom level, though the rendered size on screen changes.
Why does CSS use 96 pixels per inch?
The 96 figure is a historical convention from early desktop displays that became the fixed CSS reference. It has nothing to do with your monitor's real pixel density — the browser scales CSS pixels to physical ones for you.