Website & design
CSS Unit Converter
Convert px, rem, em, percentages, viewport units, and CSS absolute units using the context your layout actually uses.
- 14 CSS length units
- Context shown plainly
- No signup or uploads
Set the measurement
Convert a CSS length.
Runs entirely in your browser. No values are sent or stored.
Read the equivalent
Converted value
Result: 1.5rem.
24px equals 1.5rem for the context shown.
What this result used
- Root font
- 16 CSS px
Intermediate value: 24 CSS px
A property’s allowed range, browser rounding, and layout can still affect the used value. A CSS pixel is a reference pixel, not necessarily one physical device pixel.
How conversion works
Relative units need a real reference.
Relative CSS units do not have one universal pixel value. Results use the font, percentage basis, and viewport dimensions entered in the converter. Every conversion passes through a CSS-pixel equivalent without executing pasted CSS or guessing the property you meant.
| Unit family | What it depends on |
|---|---|
rem and em | The computed root or relevant element font size |
% | The property-specific quantity represented by 100% |
vw, vh, vmin, vmax | The selected viewport width and height |
in, cm, mm, q, pt, pc | Fixed CSS reference-pixel ratios |
fr distributes leftover grid space and is not a CSS length. Units such as ch, ex, cap, and icdepend on actual font metrics, so a generic numeric conversion would be misleading.
Choosing rem or em does not by itself guarantee accessibility. Test text at 200% and avoid viewport units as the only font-size basis.
Primary sources
Definitions you can verify.
Reviewed August 21, 2026. The converter follows the CSS Values and Units specification and links the accessibility guidance behind its typography note.