Pixel to REM Calculator - CSS Unit Conversion Tool
Convert between pixels and rem units for responsive web design. Set your base font size and get precise conversions instantly.
16px
⇄
8px
0.5rem
10px
0.625rem
12px
0.75rem
14px
0.875rem
16px
1rem
18px
1.125rem
20px
1.25rem
24px
1.5rem
28px
1.75rem
32px
2rem
36px
2.25rem
40px
2.5rem
48px
3rem
56px
3.5rem
64px
4rem
72px
4.5rem
Understanding PX and REM Units
Pixels (px) are fixed-size units that don't scale with user preferences. REM units are relative to the root element's font size, making them essential for accessible, responsive web design.
Why Use REM?
- Accessibility: Scales when users change browser font size.
- Consistency: One base size controls entire layout.
- Maintainability: Change root size to scale everything.
- Responsive: Adjust root size with media queries.
The Formula
- px → rem: rem = px / base
- rem → px: px = rem × base
- Default base: 16px (browser default)
The 62.5% Trick
Set html { font-size: 62.5%; } to make 1rem = 10px. This simplifies calculations: 16px = 1.6rem, 24px = 2.4rem.
When to Use Each
- REM: Font sizes, spacing, layout dimensions.
- PX: Borders, shadows, fine details.
- EM: Component-relative sizing (less common).
Responsive Typography Example
html { font-size: 16px; }
@media (max-width: 768px) {
html { font-size: 14px; }
}
/* All rem values scale automatically */