To convert millimeters to CSS pixels, this calculator uses the W3C CSS reference pixel, which defines 1 inch as exactly 96 pixels. The CSS mm unit and px unit have a fixed mathematical relationship — no physical display DPI is involved.
Enter the mm value
Enter a millimeter value. In CSS, <code>mm</code> is an absolute length unit — <code>10mm</code> in a stylesheet always equals a fixed number of CSS pixels, regardless of the device's physical screen density.
Fixed at 96 DPI
The DPI is locked at 96 because the W3C CSS specification defines 1 CSS inch as exactly 96 CSS pixels, and 1 CSS inch as exactly 25.4 mm. This creates a fixed conversion ratio.
Read the pixel result
Read the pixel result. You can use <code>{result}px</code> in place of <code>{mm}mm</code> in any CSS declaration — <code>width</code>, <code>margin</code>, <code>padding</code>, <code>border-width</code>, etc. — and the browser renders them identically.
CSS absolute units (<code>mm</code>, <code>cm</code>, <code>in</code>, <code>pt</code>, <code>pc</code>, <code>px</code>) are all defined relative to each other, not to the physical display. On high-DPI screens, browsers scale all CSS pixels uniformly via <code>devicePixelRatio</code>. The <code>mm</code> → <code>px</code> conversion stays constant.