What is the PX to REM Converter?
Modern web design relies on relative units so layouts stay flexible and accessible. The rem unit — a multiple of the root font size — lets your entire design scale when users change their browser's default text size, which is essential for accessibility and responsive typography. Converting pixels to rem by hand is tedious and error-prone, especially when the root size is anything other than the usual 16 pixels.
This converter does the math instantly. Enter any pixel value, adjust the root font size if your project uses something other than 16px, and get the exact rem value to paste into your CSS. Everything runs locally in your browser — no files are uploaded, nothing is stored, and no account is required, so you can use it as freely as a calculator.
How to use it
- Enter your pixel value — Type the px number you want to convert into the input field. Values like 14, 24.5 or 320 all work.
- Set the root font size — Keep the default 16px or change it to match your project's html font-size so the conversion is exact.
- Read the rem result — The tool divides your pixels by the root size and shows the precise rem value with full decimal accuracy.
- Copy the value — Click the copy button to grab the result, then paste it directly into your stylesheet or design tokens.
- Convert in bulk — Work through whole font-size or spacing scales quickly — the result updates live as you change either input.
Common use cases
- Switch a design system from fixed px values to scalable rem typography so text respects user accessibility settings.
- Generate rem values for a Tailwind-style spacing scale, converting 4, 8, 16, 24 and 32px into their rem equivalents.
- Recheck third-party CSS when a project sets html font-size to 62.5% so that 1rem equals 10px for easy math.
- Convert legacy pixel-based stylesheets to relative units during a site-wide accessibility or responsiveness overhaul.
Tips
- Remember that rem always refers to the root element's font size, not the nearest parent — unlike em units.
- Most browsers default the root size to 16px, so 16px equals exactly 1rem unless your CSS overrides it.
- Keep enough decimal precision when converting — 1.5625rem for 25px rounds badly if you truncate it to 1.56rem.
- Use rem for typography and spacing, but stick with px for borders and hairline details that should stay crisp.
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 becomes 24 / 16 = 1.5rem. This tool performs the division automatically.
Why use rem instead of px?
Rem units scale with the user's browser text-size setting, which helps people who need larger text and makes responsive layouts easier to maintain.
What is the default root font size?
Browsers default to 16px on the html element. If your stylesheet changes that value, enter your custom root size for correct results.
Is the converted value safe to paste into CSS?
Yes. The result is a plain numeric value with the rem suffix, such as 1.125rem, ready to paste into any stylesheet or design tool.