Pixel to REM Converter
Convert pixel values to REM/EM units based on a specified root font size (e.g., 16px).
What is the Pixel to REM Converter?
The Pixel to REM Converter is a free tool that turns CSS pixel values into rem and em units based on a root font size you choose. Enter a pixel value, set your base size (16px by default), and it shows the equivalent rem and em instantly.
REM units are calculated relative to the root html font size, which makes layouts scale predictably when a user changes their browser font setting. The converter does the division for you and also lists a reference table of common sizes so you can grab a value without typing.
It runs entirely in your browser with no signup and no data leaving your machine. Conversions update live as you type.
How to use the Pixel to REM Converter
- 1Set the Root Font Size field to your project base, which is 16px in most browsers and frameworks.
- 2Enter the pixel value you want to convert in the Pixel Value field.
- 3Read the Conversion Result card, which shows the rem and em equivalents along with the division used.
- 4Use the preset buttons (Small, Regular, Large, Extra Large) to load common values quickly.
- 5Click any size in the Common Conversions table to load it into the converter.
- 6Click the copy icon to copy the rem or em value, or press Ctrl+L to reset the fields.
What you can use it for
- Converting a design handoff measured in pixels into rem units for an accessible, scalable stylesheet.
- Migrating an existing pixel-based CSS file to rem so it respects user font size preferences.
- Checking the rem equivalent of a spacing or font-size value while writing a component.
- Working with a non-standard root font size, such as the 62.5% trick that makes 1rem equal 10px.
- Teaching or learning how the px-to-rem formula works using the shown division.
- Looking up common conversions like 24px to rem without doing mental math.
Key features
- Live conversion that updates as you type, with results shown to four decimal places.
- Adjustable root font size so you can convert against any base, not just 16px.
- A reference table of common pixel sizes with clickable values.
- One-click copy of the rem or em result.
Frequently asked questions
How do you convert px to rem?
Divide the pixel value by the root font size. With the standard 16px root, 24px divided by 16 equals 1.5rem and 8px equals 0.5rem. This converter applies that formula automatically and lets you change the root size if your project uses a different base.
What is 16px in rem?
16px equals 1rem when the root font size is 16px, which is the default in most browsers. If you change the root size, the result changes accordingly, since rem is always relative to the root.
What is the difference between rem and em?
A rem is relative to the root html element's font size, while an em is relative to the font size of the element's nearest parent. Because this tool only takes a root font size, it reports the em value using the same root-based calculation as rem.
Why should I use rem instead of px in CSS?
Rem units scale with the user's chosen browser font size, so a person who increases their default text size gets a proportionally larger layout. Fixed pixels ignore that preference, which is worse for accessibility.
Is this px to rem converter free to use?
Yes. The converter is completely free, requires no signup, and runs entirely in your browser. No values you enter are sent to a server.
Can I convert rem back to px with this tool?
This tool converts pixel input into rem and em output. To go the other way, multiply the rem value by your root font size: at a 16px root, 1.5rem times 16 equals 24px.