PX to REM Converter
Convert pixel values to REM units for your CSS, using any root font size. Free, instant, and runs entirely in your browser.
About PX to REM Converter
A pixel to rem converter solves one of the most common frustrations in responsive web development: reconciling pixel-based design mockups with rem-based CSS. Design tools like Figma and Sketch measure everything in pixels, but modern codebases increasingly size type, spacing, and layout with rem units so that everything scales when the user changes the root font size. This tool bridges that gap, letting you move between the two systems without mental arithmetic.
The math is simple but worth understanding. One rem equals the root font size, which defaults to 16px in every major browser, so the conversion is the pixel value divided by the root size: 24px becomes 1.5rem at a 16px root. Because you can set any root size, the tool stays correct for projects that define a different base on the html element, and it handles fractional pixel values precisely, so nothing is lost to rounding when you need decimal rem values.
Frontend developers use this daily when translating designs into styled components, and accessibility-minded teams use it to verify that spacing will scale for users who increase their browser font size. Designers documenting spacing tokens and students learning how CSS units behave will also find it handy. If you maintain a design system, this converter keeps your pixel-based specs aligned with the rem-based code that ships.
How to Use
- Enter the pixel value you want to convert in the Pixels field.
- Set the root font size (16px is the browser default) if your project uses a different base.
- Read the equivalent REM value instantly, then copy it with one tap.
Example
32px at a 16px root font size 2rem
REM units are always relative to the root font size, so 32 ÷ 16 = 2rem. Browsers and CSS reset frameworks commonly set the root to 16px.
FAQ
What is the difference between rem and em?
REM is relative to the root (html) font size, while EM is relative to the parent element's font size. REM is usually more predictable because it ignores the nesting depth.
Why is the default root font size 16px?
16px is the default font size of virtually all web browsers. Design systems often keep it at 16px or change it for accessibility or easier math.
Can I use this converter for fractional pixels?
Yes. Enter decimal values such as 24.5 and the tool will compute the corresponding REM value to several decimal places.
What root font size should I use?
If your CSS doesn't set a font-size on the html element, use 16px. If it does, open that rule and copy the exact value so your rem results match what renders on your live site.
Does the converter round the output?
It shows results to several decimal places so you can copy a precise value. Browsers render rem fractions exactly, so values like 1.333rem behave as intended.