Convert between pixels (px) and rem based on your root font size. Fill one or both value fields, then click calculate.
What is a rem unit?
In CSS, rem stands for “root em.” It’s a unit that scales based on the root font size (usually the html element).
If the root font size is 16px, then 1rem equals 16px, 2rem equals 32px, and 0.5rem equals 8px.
Using rem helps you build layouts and typography that are easier to scale. Instead of hard-coding every measurement in pixels, you can create a consistent system where spacing, headings, buttons, and components grow or shrink together.
Why developers prefer rem over px
1) Better accessibility
Users can change their default browser font size. When your design uses rem, many parts of your UI respond naturally to that preference, improving readability for people who need larger text.
2) Consistent scaling
With rem, a design token like 1rem means “one root unit” everywhere. This consistency makes design systems easier to maintain.
3) Cleaner responsive design
Rem units work beautifully with media queries and spacing systems. You can define a spacing scale (like 0.5rem, 1rem, 1.5rem, 2rem) and apply it throughout your project without constantly recalculating pixel values.
How to use this rem calculator
- Enter your root font size (most projects start with 16px).
- Enter either a pixel value or a rem value (or both).
- Click Calculate to see conversions instantly.
- Use the quick conversion table to reference common rem values.
Formulas used:
rem = px / root
px = rem × root
Common conversion examples (root = 16px)
- 12px = 0.75rem
- 14px = 0.875rem
- 16px = 1rem
- 20px = 1.25rem
- 24px = 1.5rem
- 32px = 2rem
Best practices for typography and spacing
Create a scale and stick to it
Pick a small set of spacing and type sizes. For example: 0.25rem, 0.5rem, 1rem, 1.5rem, 2rem, 3rem. Reusing these values creates visual rhythm and helps teams work faster.
Use px only where precision is critical
Borders, hairlines, and fine shadows often still use px. That’s normal. Many modern systems mix rem for layout/typography and px for micro-details.
Test browser zoom and default font-size changes
A strong rem-based design should remain readable at different zoom levels. Test your pages at 125%, 150%, and with larger default fonts.
Final thoughts
If you’re building a modern, accessible front-end, rem should be one of your default units. It brings consistency, scalability, and better user experience. Bookmark this calculator and use it whenever you need quick, accurate px-to-rem or rem-to-px conversion.