CSS Unit Converter
Convert between CSS units with a customizable root font size
Conversions
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Frequently asked questions
What CSS units can I convert between?
Convert between px, em, rem, pt, percent, vw, and vh. All results update instantly as you type.
Why does root font size matter?
Em, rem, and percent values are based on the root font size. Adjust it to match your project for accurate conversions.
What is the difference between em and rem?
Em is relative to the current element, while rem is relative to the root element. Rem is more predictable across a site.
How are vw and vh calculated?
Viewport units are based on the browser size: 1vw is 1 percent of viewport width and 1vh is 1 percent of height.
Which units should I use for responsive design?
Use rem for typography and spacing, percent for fluid widths, and vw or vh for full-viewport sections.
Can I copy all conversions at once?
Yes. Use the Copy All button to copy a formatted list of values.
Convert CSS units for responsive design
Translate px to rem, em, percent, and viewport units instantly. Adjust the root font size to reflect your project settings and keep layouts consistent.
Unit selection tips
- Use rem for typography and spacing to respect user settings.
- Use percent for fluid widths and container-based layouts.
- Use vw and vh for full-screen sections.
- Use px for precise borders and small UI details.
Why root font size matters
- Rem and em values scale from the root size.
- Changing the root size updates all relative units.
- Great for accessibility and global scaling.