Convert percentage values to EM units based on the parent element's font size. Essential tool for relative sizing in CSS.
How Percentage to EM Conversion Works
EM units in CSS are relative to the font size of their parent element. This tool helps you calculate the EM value that corresponds to a percentage of the parent element's font size.
The formula used for conversion is:
emValue = (percentageValue / 100) × parentFontSizeInPixels / parentFontSizeInPixels
Which simplifies to:
emValue = percentageValue / 100
Example: If you have a value of 200% with a parent font size of 16px, the EM value would be:
200% = (200 / 100) × 16px / 16px = 2em
Key Differences Between EM and REM
- EM units are relative to their parent element's font size
- REM units are relative to the root (html) element's font size
- EM units compound when nested (each level is relative to its parent)
- REM units remain consistent throughout the document
When to Use EM Units:
- When you want sizing to be relative to a component's context
- For properties that should scale with their parent's text size
- Creating scalable components that maintain proportions
- For margin and padding that should relate to the element's font size
Common Use Cases:
- Building scalable UI components
- Creating responsive typography systems
- Converting legacy percentage-based designs to relative units
- Maintaining proportional spacing within components