PX to REM Converter
Convert between pixels and REM units for responsive web design with configurable root font size.
Default is 16px (browser default)
16px = 1.0000rem (at 16px root)
font-size: 1.0000rem;padding: 1.0000rem 1.50rem;Accessibility: REM units respect user font size preferences in browser settings.
Scalability: Change root font size to scale entire design proportionally.
Maintainability: Easier to manage consistent spacing and sizing across projects.
Why Use REM Units?
REM units are relative to the root font size (html element). This makes your entire design scalable - change one value and everything adjusts proportionally.
More importantly, REM respects user preferences. If someone sets their browser to larger text, REM-based designs scale up. Pixel-based designs don't.
The Conversion
The formula is simple: rem = pixels / rootSize. With the default 16px root, 24px becomes 1.5rem.
Common conversions (16px root)
12px→0.75rem14px→0.875rem16px→1rem18px→1.125rem20px→1.25rem24px→1.5rem
When to use REM
- ✓ Font sizes
- ✓ Padding and margin
- ✓ Gap values
- ✓ Component dimensions
- ✗ Border radius (use px)
- ✗ Box shadow (use px)
Setting Your Root Size
Most browsers default to 16px, but you can set it explicitly for consistency:
html { font-size: 16px; }Some teams use 62.5% (10px) to make mental math easier - then 14px becomes 1.4rem instead of 0.875rem. This works but breaks native browser scaling.
Common Questions
REM vs EM?
EM is relative to the parent element's font size, which can compound unexpectedly. REM is always relative to root. Use REM for consistency, EM when you specifically want inheritance.
What about responsive design?
REM scales automatically when you change the root size with media queries. Combine with fluid typography techniques for fully responsive designs.
Do I need to convert everything?
No. Use REM for user-facing sizes (fonts, spacing). Keep pixels for decorative elements (borders, shadows, icons) where exact sizing matters.
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