Convert pixels to millimeters at 72, 96, 150, or 300 DPI.
Input
Reference table at 96 DPI
| Pixels | Millimeters | Inches |
|---|---|---|
| 10 px | 2.65 mm | 0.10 in |
| 50 px | 13.23 mm | 0.52 in |
| 100 px | 26.46 mm | 1.04 in |
| 500 px | 132.29 mm | 5.21 in |
| 1000 px | 264.58 mm | 10.42 in |
Details and FAQ
How does the px-to-mm formula work?
One inch equals 25.4 millimeters by international definition. DPI (dots per inch) tells how many pixels fit in one inch, so the conversion is mm = px × 25.4 ÷ DPI. Going the other way: px = mm × DPI ÷ 25.4. The result depends entirely on the DPI value you pick — a pixel has no fixed physical size on its own.
What DPI should I use — 72, 96, 150 or 300?
Use 96 DPI for modern screens (Windows, most browsers, HTML/CSS defaults). 72 DPI is the legacy macOS / classic print preview value. For print, use 150 DPI for draft output and 300 DPI for press-ready artwork, which is the standard for magazines and flyers. When preparing a design for print, ask your printer which DPI they expect.
Why do screen pixels and print millimeters differ?
Screens render at the device's pixel density (often 96 or higher on retina/hi-DPI displays), while print is a physical medium measured in millimeters. A 1080-pixel-wide image displayed at 96 DPI maps to 285.75 mm on screen, but if you print the same image at 300 DPI it only covers 91.44 mm of paper. Always match the DPI to the output medium.
How do I handle retina or 2x displays?
Retina displays typically use a device pixel ratio of 2, meaning 2 physical pixels per 1 CSS pixel. For CSS layout conversions stick with 96 DPI — CSS pixels are reference units, not physical ones. For bitmap export destined for print, export at 2x resolution and treat the output as the higher DPI (for example 192 or 300 DPI) when measuring in millimeters.
Can I use this converter for responsive web design?
Yes — designers often spec small UI elements in pixels and need a physical equivalent for print documentation, screenshots on paper, or client mockups. At 96 DPI, a 16 px body font is 4.23 mm tall, a 24 px icon is 6.35 mm, and a 320 px mobile column is 84.67 mm. Pick the DPI that matches where the mockup will be viewed.
How accurate is the conversion at different DPI values?
The math itself is exact — 25.4 mm per inch is a defined constant, so the only source of error is the DPI value you choose. If your screen reports 96 DPI but the panel actually renders at 110 DPI (common on laptops), a 100 px element will measure about 23.09 mm physically instead of the calculated 26.46 mm. For critical print work, always verify the DPI with a ruler on a printed test page rather than trusting the default screen value.
This converter turns pixel measurements into millimeters using the standard formula mm = px × 25.4 ÷ DPI. Pick the DPI that matches your output medium — 96 for screens, 300 for print — and the calculator returns the physical size in millimeters, centimeters and inches. A reference table at 96 DPI covers the common checkpoints from 10 px to 1000 px, and a custom DPI option handles hi-DPI displays or non-standard printers. Two quick examples: 100 px at 96 DPI equals 26.46 mm, handy for sizing icons on paper mockups. 1080 px at 300 DPI equals 91.44 mm, which is how wide a full-HD image lands in a press-ready layout. Copy the millimeter value with one tap for pasting into InDesign, Illustrator or a client spec.