REM PX Converter
Convert px to rem, rem to px, and tune the base font size for CSS systems that do not use the default 16px root.
Convert CSS sizes fast
Design specs almost always arrive in pixels, but production CSS increasingly uses rem because it
scales with the user's browser font settings — which is better for accessibility and makes a whole type system
easier to maintain. This converter bridges the two instantly: type a pixel value to get the rem equivalent, or a
rem value to get pixels, with both fields staying in sync as you go.
The base font size is the key variable. Most browsers default to 16px, so 1rem = 16px — but if your project sets a different root size (a common trick is 62.5% to make 1rem = 10px for easy math), just change the Base PX field and every conversion updates to match. That makes it accurate for real design systems, not just the default.
Private and instant
All conversions run locally in your browser — nothing is uploaded, and results update the moment you type.
Frequently Asked Questions
What is the default rem base?
Most browsers default to 16px, so 1rem usually equals 16px unless the root font size is changed.
Why use rem?
rem values scale with user font settings and make typography systems easier to manage.
Can I change the base?
Yes. Set any base pixel value and the conversions update immediately.
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