CSS Unit Converter
Convert between px, rem, em, pt, and percentage. Configurable base font size.
16
px
1
rem
1
em
12
pt
100
%
About CSS Units
CSS supports multiple length units for sizing elements. px is an absolute unit (1/96th of an inch). rem is relative to the root font size (usually 16px). emis relative to the parent element's font size. pt is a traditional print unit (1/72nd of an inch).
When to Use What
- rem — best for font sizes and spacing (scales with user preferences)
- px — best for borders, shadows, and fixed layouts
- % — best for widths and responsive layouts
- em — best for component-relative sizing