Css Unit Converter
Quick answer
Set a root font size, then convert px ↔ rem ↔ em for the same effective size.
For a related estimate, see Font Pairing Tool.
Explore further: Pixel Ruler Overlay · Grid Overlay Tool
em vs rem
`em` compounds with nesting—great for component-relative sizing, risky for deep trees. `rem` is stable across components.
Explore further: File Size Calculator · Accessible Color Palette
CSS units express lengths—px are absolute; rem track the root; em track the parent font. Use it when you are translating design specs into code or refactoring hard-coded px. See also Typography scale for a related utility in this cluster.
How to use this calculator
- Open the tool: Enter root font size (often 16px).
- Tune inputs: Enter a value in one unit.
- Read the output: Read equivalents and paste into your stylesheet or design tokens.
Real-world examples
- 1rem at 16px root: Equals 16px—if the user sets root to 20px, 1rem grows accordingly.
- Padding in em: Doubles if font-size doubles—useful for button chips, watch for surprises in nested cards.
Tips & gotchas
Document your root size—designers and devs must share one assumption or conversions drift.
FAQ
Does it handle viewport units?
vw/vh need viewport width/height—use them where layout context is explicit.
Does this tool send my text to a server?
Calciverse runs in your browser; we do not store your inputs on our servers for these utilities. Anything that uses network APIs (for example DNS lookup) only sends what you explicitly request.
Why do results differ from another site?
Rounding, defaults, and implementation details (color spaces, tokenizers, DNS resolvers) can differ. Compare definitions, not just the headline number.