CSS Unit Converter
Convert between px, rem, em, pt, vw, and vh using a configurable base font size and viewport. Runs entirely in your browser.
[ VALUE ]
[ BASE ]
em uses the same base font size as rem — true em cascades through parent elements, which this tool can't see.
[ OUTPUT ]
- px
- 16
- rem
- 1
- em
- 1
- pt
- 12
- vw
- 0.8333
- vh
- 1.4815
About CSS Unit Converter
CSS length units are relative to different things — rem to the root font size, vw and vh to the viewport. Converting between them requires knowing those reference values, which you set here.
How to use it
- Set the base (root) font size — 16px by default.
- Set the viewport width and height if you need vw or vh.
- Enter a value in any unit.
- Read the equivalent in every other unit.
Frequently asked questions
- What base font size should I use?
- 16px is the browser default. If you have changed the font-size on the root or html element, use that value.
- How is em different from rem?
- rem is always relative to the root font size. em is relative to the element's own font size, which varies by context — this tool uses the base value as an approximation.
- Are the conversions exact?
- px, rem, em, and pt conversions are exact for the base you set. vw and vh depend on the viewport size you enter.