Productive ToolboxPX to REM Converter
Convert pixel values to rem/em units with configurable base font size.
Formula
What is a PX to REM Converter?
A PX to REM converter is a developer tool that instantly converts pixel (px) values into rem or em units. This is essential for modern responsive web design, where rem units provide better scalability and accessibility compared to fixed pixel values.
The tool uses a simple mathematical formula: rem = px ÷ base font size. By default, the base font size is 16px, but you can customize it to match your project's requirements.
Why Use REM Units Instead of Pixels?
- Scalability: REM units scale relative to the root font size, making responsive design easier
- Accessibility: Users can adjust their browser's base font size, and rem-based layouts respect this preference
- Consistency: Using rem across your project ensures uniform spacing and sizing
- Maintainability: Changing the base font size updates all rem-based values automatically
- Mobile-Friendly: REM units adapt better to different screen sizes and zoom levels
How to Use the PX to REM Converter
- Enter your pixel values in the input field (one per line, comma-separated, or space-separated)
- Set your base font size (default is 16px, but adjust if your project uses a different base)
- Choose your output unit (REM or EM)
- View the instant conversion results
- Copy the values or CSS-ready output to your clipboard
Common PX to REM Conversions (Base 16px)
| Pixels (px) | REM Units | Common Use |
|---|---|---|
| 8px | 0.5rem | Small spacing, borders |
| 12px | 0.75rem | Small text, tight spacing |
| 16px | 1rem | Base font size |
| 20px | 1.25rem | Slightly larger text |
| 24px | 1.5rem | Headings, large text |
| 32px | 2rem | Large headings, major spacing |
| 48px | 3rem | Hero sections, large headings |
| 64px | 4rem | Extra large elements |
REM vs EM: What's the Difference?
REM (Root EM)
Relative to the root element's font size (usually the html tag). Most consistent for responsive design.
EM
Relative to the parent element's font size. Can compound if nested, making it harder to predict sizes.
Best Practices for Using REM Units
- Set a base font size: Define a clear base font size in your CSS (e.g.,
html {font-size: 16px;}) - Use REM for most properties: Apply rem to font-size, padding, margin, and width/height
- Avoid mixing units: Stick to rem throughout your project for consistency
- Test responsiveness: Verify that your layout scales correctly when users adjust their browser font size
- Use media queries: Adjust the base font size at different breakpoints for better mobile experience
Tool Features
- Real-time conversion as you type
- Batch conversion for multiple values
- Configurable base font size (8-40px)
- Support for both REM and EM units
- Reverse conversion (REM → PX)
- Copy individual values or CSS-ready output
- Quick preset buttons for common base sizes
- Conversion history with localStorage
- Mobile-responsive design
- No installation or signup required
Frequently Asked Questions
What's the default base font size?
The default is 16px, which is the standard browser default. You can change it to match your project.
Can I convert multiple values at once?
Yes! Enter values separated by commas, spaces, or on new lines, and the tool will convert them all instantly.
Is this tool free?
Yes, completely free! No ads, no signup, no hidden costs. It runs entirely in your browser.
Can I use this offline?
Yes, once loaded, the tool works offline. Your conversion history is saved locally in your browser.