CSS Unit Converter is a free math & calculators tool that runs entirely in your browser — px ↔ rem ↔ em ↔ pt ↔ %. No upload, no account, no limits.
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How to use CSS Unit Converter
Open the CSS Unit Converter tool.
Paste or type your number into the input field.
The output updates as you type — adjust the options if you need a different format.
Copy the result, or share the URL to hand the exact input to someone else.
About CSS Unit Converter
Convert CSS lengths between px, rem, em, pt and percent against a configurable root font size. Type a value in any unit and see all the equivalents, copy-ready — no more guessing what 24px is in rem.
What people use it for
Convert a px value to rem for a fluid type scale.
Translate pt from a design spec into px.
Set the root font size and convert relative units against it.
Frequently asked questions
How are rem and % calculated?
Relative to the root font size you set (default 16px); 1pt equals 1.333px at 96dpi.
Is it private?
Every calculation happens on this page, in your own browser. Your input is never sent to a server, never logged and never used for training — which also means the tool keeps working when you are offline.