CSS Unit Converter
Convert between CSS units: px, rem, em, vh, and vw.
Output will appear here...About CSS Unit Converter
The CSS Unit Converter translates between px, rem, em, vh, and vw using a base font size you set, so you can move from fixed pixels to relative, accessible units with confidence. Relative units scale with user settings and viewport size, which is key for responsive, accessible design. Conversion runs locally in your browser with nothing uploaded. For color work, see the Color Picker and HEX to RGB tools.
How to Use
- 1Open CSS Unit Converter and paste or type your data into the input area.
- 2Adjust any available options to match the result you want.
- 3Your output is generated instantly — no button-clicking required for most tools.
- 4Use the Copy or Download button to save your result.
Common Use Cases
- Converting colors between HEX, RGB, and HSL for CSS
- Generating gradients, shadows, and border-radius values
- Building consistent design tokens for a UI
- Converting units like px, rem, and em for responsive design
Frequently Asked Questions
How is px to rem calculated?
rem is relative to the root font size, so the converter divides your pixel value by the base size you set — typically 16px — to give the equivalent rem, and reverses it the other way.
Why use rem and em instead of px?
Relative units respect the user's font-size preferences and scale better across devices, improving accessibility and making responsive layouts easier to maintain than fixed pixels.
Is CSS Unit Converter free to use?
Yes. CSS Unit Converter is completely free with no sign-up, no subscription, and no usage limits. Every tool on CodeUtilityKit is free forever.
Is my data safe when I use CSS Unit Converter?
Absolutely. CSS Unit Converter runs entirely in your browser. Your input is processed locally with JavaScript and is never sent to, stored on, or logged by any server — so it is safe even for private or sensitive data.
Features
- Run CSS Unit Converter instantly, right in your browser
- 100% private — your data never leaves your device
- Copy the result to your clipboard in one click
- Free and unlimited with no account or sign-up
- Clear, friendly error messages when something is wrong
- Works on desktop and mobile, even offline after first load
Related Tools
Related tools: Color Picker.