About EM to Percentage Conversion
This tool converts EM units (relative to parent font size) to percentage units (relative to parent element size). Both are relative units but serve different purposes in responsive design.
How to Use This Tool
- Enter the EM value you want to convert
- Specify the parent element's font size in pixels
- Specify the parent element's size in pixels (width/height)
- Click "Convert to Percentage" to get the equivalent % value
- Copy the result and use it in your CSS
The Conversion Formula
The formula to convert EM to percentage is:
percentage = (em × parent-font-size) / parent-size × 100%
For example, to convert 1.5em to percentage when parent font is 16px and parent size is 200px:
(1.5 × 16) / 200 × 100% = 12%
Why Convert EM to Percentage?
- Fluid Layouts: Create elements that scale with their container
- Responsive Components: Build components that adapt to different contexts
- Legacy Support: Work with older code that uses percentages
- Precise Scaling: Achieve exact proportional relationships
Key Differences Between EM and Percentage
- EM is relative to the parent element's font size
- Percentage is relative to the parent element's size
- EM is typically used for typography and vertical spacing
- Percentage is often used for widths, heights, and horizontal spacing
- EM values compound in nested elements, percentages don't
Best Practices
- Use EM for typography and vertical rhythm
- Use percentage for fluid layouts and container-relative sizing
- Combine with min/max values to prevent extreme scaling
- Test your conversions at different viewport sizes
- Document your unit strategy for maintainability