Pixel To mm Converter
A designer hands over a layout in pixels, the printer wants millimetres, and the bridge is a single division by PPI and a multiplication by 25.4.
Quick answer: divide the pixels by the PPI, then multiply by 25.4. At 96 PPI, 1 px is about 0.2646 mm and 100 px is 26.46 mm, while at 300 PPI, 100 px is only 8.47 mm.
The pixel to millimetre formula
Pixels divided by PPI gives inches, and one inch is exactly 25.4 mm, so multiply by 25.4 to reach millimetres (Imageonline: Pixel to mm converter).
The result depends on PPI, so always say which density you used.
For 100 px at 96 PPI, 100 ÷ 96 is 1.0417 in, and 1.0417 × 25.4 is 26.46 mm.
For 100 px at 300 PPI, 100 ÷ 300 is 0.3333 in, which is 8.47 mm.
Pixels, PPI and the millimetre
The millimetre is a physical unit, while a pixel is a dot of a screen or image. PPI links the two by counting pixels in one inch, which is exactly 25.4 mm.
At 96 PPI, the usual web benchmark, one pixel is 25.4 ÷ 96, or about 0.2646 mm (Omni Calculator: Pixels to inches converter).
Preset densities of 72, 96, 150, 300 and 600 are common in converters (Imageonline: Pixel to mm converter).
How to convert pixels to mm step by step
- Find the PPI of your screen or print file.
- Divide the pixels by that PPI to get inches.
- Multiply the inches by 25.4.
- Round to two decimals.
Example 1: 100 px on the web
- Start with 100 px at 96 PPI.
- 100 ÷ 96 = 1.0417 in.
- 1.0417 × 25.4 = 26.46 mm.
100 px = 26.46 mm
Example 2: an A4 page at 300 PPI
- A4 is 210 mm wide.
- 210 ÷ 25.4 × 300 = 2,480 px.
- The page is 2,480 px wide.
210 mm = 2,480 px
Example 3: 1,000 px at 150 PPI
- Start with 1,000 px at 150 PPI.
- 1,000 ÷ 150 = 6.667 in.
- 6.667 × 25.4 = 169.3 mm.
1,000 px = 169.3 mm
On screens the real size varies, because phones and monitors scale pixels differently.
pixels to mm conversion table
| Pixels | 72 PPI | 96 PPI | 300 PPI |
|---|---|---|---|
| 1 px | 0.35 mm | 0.26 mm | 0.08 mm |
| 10 px | 3.53 mm | 2.65 mm | 0.85 mm |
| 50 px | 17.64 mm | 13.23 mm | 4.23 mm |
| 100 px | 35.28 mm | 26.46 mm | 8.47 mm |
| 200 px | 70.56 mm | 52.92 mm | 16.93 mm |
| 500 px | 176.39 mm | 132.29 mm | 42.33 mm |
| 800 px | 282.22 mm | 211.67 mm | 67.73 mm |
| 1,000 px | 352.78 mm | 264.58 mm | 84.67 mm |
| 1,920 px | 677.33 mm | 508 mm | 162.56 mm |
The highlighted row is 100 px. Compare the columns to see how density shrinks the millimetre size.
A quick mental shortcut for pixels to mm
At 96 PPI, multiply the pixels by about 0.26, so 100 px is 26 mm. At 300 PPI, multiply by about 0.085, so 100 px is 8.5 mm.
To go the other way at 96 PPI, divide the millimetres by 0.2646.
Mm to pixels
Reverse the formula by dividing the millimetres by 25.4 and multiplying by the PPI. So 50 mm at 300 PPI is 50 ÷ 25.4 × 300, or about 591 px.
A4 paper, 210 by 297 mm, is 2,480 by 3,508 px at 300 PPI.
Screen pixels versus real size
A CSS or design pixel is a reference unit, not a fixed physical size, so a 100 px box may measure slightly more or less than 26 mm on a real screen. Zoom, display scaling and device density all change it.
For true physical size, convert at the actual PPI of the device or the print file.
Pixel to mm for print and CAD work
Print designers set artwork in pixels, then confirm the size in millimetres before sending it to a printer. Engineers and makers do the same with scanned drawings.
Writing the PPI beside every conversion prevents costly mismatches.
Checking your answer
Divide the millimetres by 25.4 and multiply by the PPI to recover the pixels. If you get your starting number, the conversion is right.
A higher PPI should always give a smaller millimetre result for the same pixels.
A print example
A 1,080 pixel side at 300 PPI is 91.44 mm long. At 96 PPI it is 285.8 mm.
A thin line
A 4 pixel line at 96 PPI is about 1.06 mm thick. That matters if a printer needs a minimum line width.
Quick conversion answers
| Conversion | Result |
|---|---|
| 1 pixel to mm | 0.2646 mm at 96 PPI |
| 10 pixels to mm | 2.65 mm at 96 PPI |
| 50 pixels to mm | 13.23 mm at 96 PPI |
| 100 pixels to mm | 26.46 mm at 96 PPI |
| 500 pixels to mm | 132.3 mm at 96 PPI |
| 1,000 pixels to mm | 264.6 mm at 96 PPI |
Where this conversion is used
Designers and printers match screen artwork to physical sizes.
Engineers and makers scale scanned drawings and images.
Developers and students convert interface pixels to real units.
Common mistakes to avoid
- Skipping PPI. Pixels alone do not give millimetres.
- Using 25 instead of 25.4. That adds a 1.6 percent error.
- Assuming screens are exact. Real screens scale pixels differently.
- Multiplying instead of dividing by PPI. More PPI means smaller millimetres.
Related converters
Frequently asked questions
How many mm is one pixel?
About 0.2646 mm at 96 PPI.
How do I convert pixels to mm?
Divide the pixels by the PPI, then multiply by 25.4.
How many mm is 100 pixels?
26.46 mm at 96 PPI, or 8.47 mm at 300 PPI.
How do I convert mm to pixels?
Divide the millimetres by 25.4 and multiply by the PPI.
How many pixels is A4 at 300 PPI?
About 2,480 by 3,508 pixels.
Is a pixel the same size on every screen?
No. It depends on the PPI of the device.
Sources
- Imageonline: Pixel to mm converter (imageonline.co)
- Omni Calculator: Pixels to inches converter (omnicalculator.com)
- Elementor: PX to inches converter (elementor.com)
