About

Units converts CSS lengths in the browser. Rem is divided or multiplied by the root font size. Em uses the parent font size. Both start at 16, the usual browser default, so the two match until you change one of them.

Absolute units (pt, pc, cm, mm, in) go through the CSS pixel, where 1in is 96px. Percent uses a parent size you type. vw, vh, vmin, and vmax use a viewport width and height you type. ch, ex, and lh use reference sizes you can edit, because this page cannot measure your font. dpi, dppx, and dpcm convert among themselves, with 1dppx equal to 96dpi.

The numbers stay on your device. There is no account and no saved history.