MM to PX

The MM to PX calculator converts millimeters (mm) to pixels (px) by applying a DPI-based conversion factor. Millimeters are physical length units defined by the International System of Units. Pixels are digital screen units whose physical size changes based on DPI (Dots Per Inch), also called PPI (Pixels Per Inch).

The calculator performs 3 steps to convert mm to px:

1. Read the DPI value — Select from 4 standard presets (72, 96, 150, 300 DPI) or enter a custom resolution.
2. Calculate the conversion factor — Divide DPI by 25.4, the exact number of millimeters in one international inch (25.4 mm = 1 in). This produces the pixels-per-millimeter ratio.
3. Multiply mm by the factor — The millimeter input × pixels-per-mm ratio = the pixel output.

The World Wide Web Consortium (W3C) defines the Cascading Style Sheets (CSS) reference pixel at 96 DPI. Håkon Wium Lie, co-creator of CSS, established this standard so that 1 inch on screen equals exactly 96 pixels. At 96 DPI, the conversion factor is 96 ÷ 25.4 = 3.7795275591 pixels per millimeter.

On a retina display, the device pixel ratio is 2× or 3×, meaning 2 or 3 hardware pixels render each CSS pixel. The MM to PX calculator outputs CSS pixels, which remain consistent across screen resolutions. Responsive web design relies on CSS pixels to keep layouts stable across devices with different pixel densities.

The mm to px conversion runs instantly in the browser with no server processing. Enter a value in the millimeters field, select a DPI setting, and read the pixel result. Enter pixels instead to reverse the calculation and convert px back to mm.

px = mm × (DPI ÷ 25.4) is the mm to px conversion formula. The constant 25.4 represents the exact number of millimeters in 1 inch (25.4 mm = 1 in). DPI (Dots Per Inch) defines how many pixels fit into one inch of screen or print space.

The formula contains 3 components:

• mm — the millimeter input value (the physical length to convert)
• DPI — the target resolution in dots per inch (72, 96, 150, or 300)
• 25.4 — the constant that converts inches to millimeters

At the CSS standard of 96 DPI, the conversion factor is 96 ÷ 25.4 = 3.7795275591 pixels per millimeter. Adobe Photoshop, Figma, and Sketch all use this formula when converting between physical and pixel-based units. Print design workflows use 150 DPI or 300 DPI for higher pixel density output.

Worked examples at 4 standard DPI values

Each example converts 10 mm using a different DPI setting:

• 72 DPI (Mac Classic / web legacy): 10 × (72 ÷ 25.4) = 10 × 2.8346 = 28.3465 px
• 96 DPI (Windows / CSS standard): 10 × (96 ÷ 25.4) = 10 × 3.7795 = 37.7953 px
• 150 DPI (medium resolution print): 10 × (150 ÷ 25.4) = 10 × 5.9055 = 59.0551 px
• 300 DPI (high quality print): 10 × (300 ÷ 25.4) = 10 × 11.8110 = 118.1102 px

The formula stays the same for any DPI value. Use 96 DPI for responsive web design in Google Chrome, Mozilla Firefox, or Apple Safari. Use 300 DPI for print-quality images and PDF export. The mm to px conversion tool accepts any positive DPI value, so enter the exact resolution required by your project.

At 96 DPI, 1 millimeter (mm) equals 3.7795 pixels (px). The pixel count per millimeter changes based on the screen resolution or print resolution measured in DPI (Dots Per Inch).

There are 4 standard pixels-per-millimeter values:

• 72 DPI: 1 mm = 2.8346 px (2.8346 pixels per millimeter)
• 96 DPI: 1 mm = 3.7795 px (3.7795 pixels per millimeter)
• 150 DPI: 1 mm = 5.9055 px (5.9055 pixels per millimeter)
• 300 DPI: 1 mm = 11.8110 px (11.8110 pixels per millimeter)

The formula to calculate pixels per millimeter is: pixels per mm = DPI ÷ 25.4. The constant 25.4 is the exact number of millimeters in 1 inch.

In CSS, the W3C specification fixes the reference pixel at 96 DPI. MDN Web Docs documents the CSS mm unit as an absolute length unit where 1 mm = 3.7795275591 px. Chrome DevTools displays computed values in pixels, so knowing the mm-to-px conversion factor helps when debugging layouts that mix physical and digital units.

The pixel-per-millimeter ratio increases with DPI. Higher DPI means more pixels per inch, which means more pixels per millimeter. A 300 DPI print file contains 4.17× more pixels per millimeter than a 72 DPI screen display (11.8110 ÷ 2.8346 = 4.17).

Yes, convert mm to pixels by multiplying the mm value by (DPI ÷ 25.4). The mm to px conversion works for any positive millimeter value and any DPI setting.

There are 3 ways to convert mm to pixels:

1. Use this MM to PX calculator — Enter a millimeter value above, select a DPI, and read the pixel result instantly.
2. Apply the formula manually — Multiply mm × (DPI ÷ 25.4). For example, 25 mm at 96 DPI = 25 × 3.7795 = 94.4882 px.
3. Use design software — Adobe Photoshop, Figma, and Sketch each have built-in unit conversion that applies the same formula automatically.

Use 96 DPI for standard web and Cascading Style Sheets (CSS) work. Use 300 DPI for print design and high-resolution image export. The conversion is bidirectional: divide pixels by (DPI ÷ 25.4) to convert px back to mm.

The mm to px conversion applies in Adobe Photoshop when setting image dimensions, in Figma when translating physical specifications to screen units, and in Sketch when designing for specific print sizes. The viewport size in responsive web design uses CSS pixels, making the mm to px conversion tool useful when bridging print mockups and digital layouts.