CSS Unit Converter
Free CSS unit converter: convert px, rem, em, vw, vh, % locally in your browser. Set root font size and viewport width. No upload, no account required.
Runs locally in your browser. Your input is not uploaded to DevToolMate servers.
Developer Quick Tips
- Convert rem to px by entering the rem value and setting your root font size (default 16px) to match your project's CSS assumptions.
- Test responsive units by setting viewport width to your target breakpoint, then check vw, vh, and % equivalents instantly.
- Enter any amount and unit to see all equivalent values across px, rem, em, vw, vh, and % without reading live DOM styles.
- Verify viewport scaling across device sizes by adjusting the viewport width setting before applying responsive breakpoints.
- Use em and rem interchangeably in this tool; both use the configured root font size for predictable, consistent conversions.
Frequently asked questions
How do I convert rem to px using this tool?
Enter the rem value and set your root font size (default 16px) to match your project's CSS. The converter shows the px equivalent instantly. Adjust root font size to match your stylesheet assumptions for accurate conversions.
How do I convert CSS units for responsive design?
Set viewport width to your target breakpoint (default 1280px), enter any value and unit, and the tool shows vw, vh, and % equivalents. Test responsive scaling across different device sizes without reading live DOM styles.
What CSS units does this converter support?
CSS Unit Converter supports px, rem, em, vw, vh, and %. It does not convert physical units like pt, cm, in, or ch, and does not account for zoom or device pixel ratio.
Does CSS Unit Converter upload my data?
No. CSS Unit Converter runs locally in your browser. Your input is not uploaded to DevToolMate servers for processing.
What's the difference between em and rem in this converter?
Both use the same root font size setting for predictable math. This tool treats em as rem for consistent conversions and does not read computed styles from the live DOM.
Is this CSS unit converter free to use?
Yes. CSS Unit Converter is free with no account required. All processing stays on your device.
Will my input be stored after I close the tab?
No. Input stays in memory for the current session. Closing the tab clears it. Theme preference is stored locally in your browser and is not tool input.
Related tools
- rem to px Converter: Convert rem to px or px to rem with custom root font size. Enter 1.25rem, 3rem, or any value and get instant results in your browser - no upload, no account.
- Aspect Ratio Calculator: Free aspect ratio calculator for CSS aspect-ratio property. Enter 16:9 or pixel dimensions to get simplified ratios, CSS declarations, and responsive sizing, all in your browser, no upload.