↔

Pixels ↔ REM/EM Converter

Convert between px, rem, and em CSS units. Set your base font size for accurate conversion.

Base Font Size
px
💡 Definition

CSS Units: PX, REM, EM

  • PX are absolute pixel units.
  • REM is relative to the root (html) font-size.
  • EM is relative to the parent element's font-size.
  • Using REM/EM creates more accessible, scalable designs.
📖 How to use

Step by Step

  • Set your base font size (default 16px)
  • Enter a value in any field — others update
  • A quick reference table shows common sizes
  • All conversions are bidirectional
🎯 Use cases

When to use

  • Responsive web design
  • Accessibility-compliant typography
  • CSS framework customization
  • Design system token creation

Frequently Asked Questions

What's the difference between REM and EM?▾
REM is always relative to the root (html) font-size. EM is relative to the parent element's font-size. REM is more predictable; EM can compound when nested.
Why use REM instead of PX?▾
REM respects user browser settings. If a user increases their default font size for accessibility, REM-based layouts scale proportionally while PX stays fixed.

Related Tools