REM to MM Converter
Conversion Guide
1. Convert rem to px (multiply by root font size). 2. Convert px to mm. Example: 1rem = 16px ≈ 4.23mm
REM to MM Conversion Table
| REM | 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 REM?
The rem (root em) unit is a relative unit that's always based on the font-size of the root element (html). This makes it powerful for creating consistent, scalable layouts that respect user preferences. Unlike em units which compound in nested elements, rem always refers back to the root font-size.
Why should I use rem instead of pixels?
REM units provide better accessibility by respecting user font size preferences, maintain consistent scaling across the site, and simplify responsive design. Unlike pixels, rem units scale proportionally when users change their browser's font size settings.
How do I calculate rem values from pixels?
To convert pixels to rem, divide the desired pixel value by the root font size (typically 16px). For example: 32px ÷ 16px = 2rem. Many code editors and dev tools can do this calculation automatically.
What's the difference between rem and em units?
While both are relative units, em is relative to the font-size of the current element or its closest parent with a defined font-size. rem is always relative to the root element, making it more predictable for layout and preventing compound scaling issues.
When should I use rem vs em units?
Use rem for consistent spacing, layout and general typography. Use em when you want elements to scale relative to their parent's font size, like padding in buttons or line-height in paragraphs.
How can I debug rem calculations?
Most browser dev tools can show both rem and pixel values. You can also set a more convenient root font-size (like 10px) to make calculations easier: html { font-size: 62.5%; } (making 1rem = 10px)
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 REM to MM?
To convert REM to MM, use the following formula:
(rem * root font size) / 3.78