MM to Pixels Converter
This free mm to pixels converter turns millimeters into pixels (and pixels back into millimeters) instantly, using the web standard of 96 DPI by default. Because pixels depend on resolution, you can switch the DPI to match your destination — 96 for screens, 300 for print. The conversion is bidirectional, so type a value in either field to see the other update. Everything runs entirely in your browser: nothing is uploaded, and there is no signup, so your measurements stay private.
How to use the mm to pixels converter
- Type the measurement you want to convert into the Millimeters field (decimals like 12.5 are fine).
- Choose your DPI (resolution): pick 96 for on-screen and web work, or 300 for print.
- Read the result in the Pixels field — it updates as you type.
- To go the other way, enter a value in the Pixels field and the converter shows the equivalent millimeters.
- Adjust the DPI at any time to instantly recalculate for a different output.
The tool runs 100% in your browser, so your measurements are never uploaded, stored, or shared.
The mm to pixels formula
Millimeters convert to pixels through the inch, because pixels-per-inch (DPI) is defined against inches and there are exactly 25.4 mm in 1 inch:
pixels = mm × (DPI ÷ 25.4)
At the web standard of 96 DPI, one millimeter is 96 ÷ 25.4 = 3.7795 px. To reverse the calculation, divide back out:
mm = pixels × 25.4 ÷ DPI
Worked examples at 96 DPI:
- 1 mm × (96 ÷ 25.4) = 3.78 px
- 10 mm × (96 ÷ 25.4) = 37.8 px
- 50 mm × (96 ÷ 25.4) = 189 px
- 210 mm × (96 ÷ 25.4) = 793.7 px (A4 width)
The same measurements at 300 DPI (print) produce far larger pixel counts — 1 mm = 11.81 px, and 210 mm = 2480 px — which is exactly why you must set the right DPI before converting. Remember: 1 inch = 25.4 mm, so that constant sits inside every mm-to-pixel calculation.
Why DPI (resolution) matters
There is no single “correct” number of pixels in a millimeter, because pixels-per-inch is resolution-dependent. The same 1 mm is 3.78 px on a standard web page but 11.81 px in a print-ready file. Pick the DPI that matches where the image will be used:
- 96 DPI is the CSS/web default. Use it for websites, UI mockups, screen graphics, and anything viewed on a monitor. (72 DPI is a legacy value where 1 mm ≈ 2.835 px.)
- 300 DPI is the standard for print. Use it for photos, flyers, business cards, and anything sent to a printer, so the output stays crisp instead of pixelated. (150 DPI, where 1 mm ≈ 5.906 px, is a common draft or large-format value.)
The rule of thumb: always match the DPI to the destination. Designing 300 DPI print artwork at 96 DPI will leave it too small and soft, while sizing a web graphic at 300 DPI makes it needlessly huge.
MM to pixels conversion table
| Millimeters | Pixels @96 DPI | Pixels @300 DPI |
|---|---|---|
| 1 | 3.78 | 11.81 |
| 2 | 7.56 | 23.62 |
| 5 | 18.9 | 59.06 |
| 10 | 37.8 | 118.1 |
| 25 | 94.5 | 295.3 |
| 50 | 189 | 590.6 |
| 100 | 377.95 | 1181.1 |
| 210 | 793.7 | 2480 |
| 297 | 1122.5 | 3508 |
A-paper sizes in millimeters converted to pixels
ISO A-series paper is defined in millimeters, so this converter is handy for setting up print documents. Using pixels = mm × (DPI ÷ 25.4), here are the common sizes at both resolutions:
- A4 (210 × 297 mm) = 794 × 1123 px at 96 DPI, or 2480 × 3508 px at 300 DPI.
- A5 (148 × 210 mm) = 559 × 794 px at 96 DPI, or 1748 × 2480 px at 300 DPI.
- A3 (297 × 420 mm) = 1123 × 1587 px at 96 DPI, or 3508 × 4961 px at 300 DPI.
Business-card and print-bleed sizes in pixels
Small print jobs are also specified in millimeters. A standard European business card is 85 × 55 mm, which is 1004 × 650 px at 300 DPI. Printers usually ask for 3 mm of bleed on each edge, so an 85 × 55 mm card becomes 91 × 61 mm with bleed — roughly 1075 × 720 px at 300 DPI. Convert your trim size plus bleed in millimeters here to get the exact pixel canvas to build in Photoshop, Canva, or Figma.
Frequently asked questions
How many pixels is 1 mm?
At the web/CSS standard of 96 DPI, 1 mm = 3.78 pixels (96 ÷ 25.4 = 3.7795). At 300 DPI for print, 1 mm = 11.81 pixels. The exact number depends on the resolution you choose because pixels-per-inch is resolution-dependent.
How do I convert mm to pixels?
Multiply the millimeters by the DPI divided by 25.4: pixels = mm × (DPI ÷ 25.4). For example, 10 mm at 96 DPI is 10 × (96 ÷ 25.4) = 37.8 px. This converter does the math for you and also reverses it with mm = pixels × 25.4 ÷ DPI.
How many pixels is 210 mm?
210 mm (the width of A4 paper) is 793.7 px at 96 DPI and 2480 px at 300 DPI. Use the 300 DPI figure when preparing an A4 document for print, and the 96 DPI figure for on-screen layouts.
Why does DPI change the result?
Because pixels-per-inch is resolution-dependent, and DPI sets how many pixels fill one inch (and therefore each 25.4 mm). The same 50 mm is 189 px at 96 DPI but 590.6 px at 300 DPI. If your numbers look off, check that the DPI setting matches the resolution you actually need.
Why is there a 25.4 in the formula?
Because 1 inch equals exactly 25.4 mm. DPI (dots per inch) is defined against inches, so to use it with millimeters you divide the DPI by 25.4 to get pixels-per-millimeter, then multiply by your measurement.
How do I convert pixels back to mm?
Multiply the pixel count by 25.4 and divide by the DPI: mm = pixels × 25.4 ÷ DPI. For instance, 378 px at 96 DPI is 378 × 25.4 ÷ 96 = 100 mm. Enter a value in the Pixels field and the converter shows the millimeters automatically.
What DPI should I use for web images?
Use 96 DPI, the CSS and web default. Screens render in pixels, so a graphic that is 189 px wide displays the same regardless of its stored DPI — 96 keeps the mm-to-pixel math consistent with how browsers measure an inch.
What is the difference between DPI and PPI?
For this conversion they mean the same thing: how many pixels fit in one inch. PPI (pixels per inch) technically describes digital images and screens, while DPI (dots per inch) comes from printing, but both drive the mm × (DPI ÷ 25.4) formula the same way.