EM to MM Converter
Conversion Guide
1. Convert em to px (multiply by parent element font size). 2. Convert px to mm. Example: 1em = 16px ≈ 4.23mm
EM to MM Conversion Table
| EM | MM | Actions |
|---|---|---|
| 1 | 4.2333 | |
| 2 | 8.4667 | |
| 3 | 12.7 | |
| 4 | 16.9333 | |
| 5 | 21.1667 | |
| 6 | 25.4 | |
| 8 | 33.8667 | |
| 10 | 42.3333 | |
| 15 | 63.5 | |
| 20 | 84.6667 | |
| 25 | 105.8333 |
Frequently Asked Questions
Basics
What is EM?
The em unit creates sizes that adapt to their parent element's font size - like a family inheritance system for measurements. When you use 1em, you're saying 'make this the same size as my parent's font'. Using 2em means 'make this twice my parent's font size'. This makes em units perfect for creating harmonious, scalable designs.
I set my element to 1.5em but it's bigger than expected. What's happening?
Em units cascade - if your parent element is already 1.2em, then 1.5em will actually be 1.5 times that increased size. This compound effect is both powerful and sometimes tricky to manage.
Should I use em for padding and margins too?
Yes! Using em for padding and margins helps maintain proportional spacing as font sizes change. For example, button padding of 1em will grow naturally with the button's text size.
My nested elements keep getting bigger and bigger with em. Help!
This is the cascading effect of em units. Each nested element multiplies the parent's size. Consider using rem for deeper nested elements or reset sizes at specific levels if this isn't desired.
When should I use em vs rem vs px?
Use em when you want elements to scale with their parent's font size (like component internals), rem when you want scaling based on root font size (like headers), and px for truly fixed sizes (like borders).
What is MM?
Millimeters (mm) are absolute-length units that correspond to physical millimeters, primarily used in print design.
How accurate are mm units on screens?
The accuracy of mm units on screens depends on the device's DPI settings and physical characteristics. They're more reliable in print.
When should I use mm?
Use mm in print stylesheets or when designing for international markets that use the metric system.
Conversion
How to convert EM to MM?
To convert EM to MM, use the following formula:
(em * parent font size) / 3.78