01
px to rem
16px at a 16px base font size equals 1rem — the most common everyday conversion.
CSS Unit Converter
ConvertersConvert CSS units — px to rem, em, pt, % and more — with a custom base font size — free online.
em and % are relative to a parent element's font size in real CSS — this treats the base font size you enter as that parent value.
About
About the CSS Unit Converter
Converts a CSS length value between px, rem, em, pt, pc, in, cm, mm and percent, using a base font size you set, and shows the equivalent value in every one of those units at once.
Front-end developers use it to convert a design's pixel measurements into rem values for a stylesheet, while designers use it to check what a font size in points or picas translates to on screen. It's part of Toolapt's broader lineup of free converters, open to everyone with no account and no limit on repeat runs.
Examples
CSS Unit Converter examples
2 worked examples
02
A larger heading
32px at a 16px base equals 2rem, or 24pt.
Related tools
FAQ
Frequently asked questions
Quick answers to common questions about the CSS Unit Converter.
What does the CSS Unit Converter do?
It converts a value between px, rem, em, pt, pc, in, cm, mm and percent, using a base font size you set, and shows the equivalent value in every one of those units.
Is the CSS Unit Converter free to use?
Yes. It's free, with no sign-up, no watermark and no limit on how many times you use it.
Is my input safe when I use this tool?
Yes. The value and base font size you enter are processed entirely on your own device — nothing is sent to a server.
What is the base font size for?
rem, em and percent are all relative units — they only have a concrete pixel size once you know the font size they're relative to. The base font size field lets you set that reference value instead of assuming a fixed default.
What's the difference between rem and em here?
In real CSS, em is relative to its own element's font size while rem is always relative to the root element's font size; since this tool works with a single base value, it treats both as relative to the base font size you enter.
Why would I convert to physical units like in, cm or mm?
Those come in handy for print stylesheets or any design work where a length needs to correspond to an actual physical measurement rather than a screen-relative one.
Can I use the CSS Unit Converter on my phone?
Yes. The page is fully responsive and works on mobile, tablet and desktop browsers alike.
Does the CSS Unit Converter have any limitations?
It covers the standard CSS length units; it doesn't include viewport-relative units like vw or vh, since those depend on the browser window size rather than a font size.