1 CSS pixel = 0.0625 rem
CSS defines its absolute units against a reference pixel of 1/96 inch, so px, pt, pc, in, cm and mm all convert exactly — one inch is 96 px, one point is 4/3 px. Font-relative units are the exception: rem and em depend on the root font size, which defaults to 16 px in every browser but is frequently changed. The root font size is editable on the live converter so a design system on a 10 px or 62.5 percent root converts correctly.
Formula rem = px ÷ root font size (default 16)
| CSS pixel | Root em |
|---|---|
| 1 px | 0.0625 rem |
| 2 px | 0.125 rem |
| 3 px | 0.1875 rem |
| 5 px | 0.3125 rem |
| 10 px | 0.625 rem |
| 25 px | 1.5625 rem |
| 50 px | 3.125 rem |
| 100 px | 6.25 rem |
| 250 px | 15.625 rem |
| 500 px | 31.25 rem |
| 1000 px | 62.5 rem |
Related guides: Digital and print layout units: px, rem, em, points and DPI