Free Pixels to REM Converter for CSS
Modern responsive web design relies heavily on relative units like rem instead of fixed pixel values. But if you have been working in pixels for years, converting to rem in your head gets tedious fast. Our free px to rem converter does the math instantly — enter a pixel value, get the rem equivalent, and vice versa. You can even customize the root font size if your project uses something other than the standard 16px.
Stop doing mental division and start converting with confidence. This tool is designed for frontend developers who want to build accessible, scalable interfaces.
How to Use the PX to REM Converter
Enter a pixel value to see the rem equivalent, or enter a rem value to see the pixel equivalent. Set your base font size (default is 16px) to match your project's root font size. The conversion updates in real time as you type. Copy the result and use it directly in your CSS.
Why Use REM Instead of Pixels?
Rem units are relative to the root font size, which means they automatically scale when users change their browser's default font size. This is crucial for accessibility — users with visual impairments often increase their browser font size, and rem-based layouts respect that preference. Pixel values, on the other hand, are fixed and do not scale.
- Frontend developers build responsive layouts that scale proportionally.
- Accessibility-focused teams ensure their designs respect user font size preferences.
- Design system maintainers create consistent spacing and typography scales.
- CSS-to-Tailwind migrators convert pixel-based designs to rem-based utility classes.
Key Features
- Bidirectional conversion: px to rem and rem to px
- Customizable root font size (default 16px)
- Real-time conversion as you type
- Clean, simple interface for quick lookups
- Free with no sign-up required
Quick Reference
With a 16px root font size: 8px = 0.5rem, 12px = 0.75rem, 14px = 0.875rem, 16px = 1rem, 18px = 1.125rem, 20px = 1.25rem, 24px = 1.5rem, 32px = 2rem, 48px = 3rem, 64px = 4rem. Bookmark this tool for quick lookups whenever you are writing CSS.
Frequently Asked Questions
What is 1 rem equal to?
1 rem equals the root font size of the document. By default, browsers set this to 16px, so 1rem = 16px. If you change the root font size (e.g., html { font-size: 10px; }), then 1rem = 10px.
What is the difference between rem and em?
Rem is relative to the root (html) font size and stays consistent throughout the document. Em is relative to the font size of its parent element, which can compound when elements are nested. Rem is generally preferred for layout sizing because it is more predictable.
Should I use rem for everything in CSS?
Use rem for font sizes, spacing, and layout dimensions. Use pixels for borders, box shadows, and very small details where scaling would not improve the experience. Some properties like border-radius work well in either unit. The key is consistency within your project.