CSS Unit Converter

rem always uses root font size. em uses the parent font size above — if that parent is itself sized in em relative to its own parent, the real value compounds further up the tree than this one level.

Percentage reference size (px)

% has no single meaning in CSS — width: 50% is relative to the containing block's width, font-size: 150% to the parent's font size, and others differ again. Put whichever of those applies here.

For a value that should change smoothly between two viewport widths, see the Fluid Type / clamp() Calculator — this tool converts one snapshot at a time, on purpose.

The six absolute units — pt, pc, in, cm, mm, q — convert to px using CSS's own fixed 96px = 1in definition, not any real screen's actual pixel density.