CSS Unit Converter

Convert px ↔ rem and px ↔ em with a configurable root font size.

px / rem / em

Instant conversion · browser-only

● Ready

Root font size (px)

Pixels (px)

rem

Pixels (px)

em (parent = root)

What is the difference between rem and em?

rem is relative to the root (html) font size. em is relative to the parent element’s font size.

Most browsers use 16px as the default root font size, so 1rem typically equals 16px unless you change html { font-size }.