The PX to REM Converter turns pixel values into rem units, which are relative to the root (html) font size. Rem gives you scalable, accessible sizing that stays consistent across your whole page.
Because rem is tied only to the root font size, it removes the guesswork of nested units and is the go-to choice for building interfaces that scale cleanly from a single setting. Enter a pixel value and the converter gives you the rem equivalent (and back again) instantly.
How to convert px to rem
- Enter the pixel value.
- Set the root font size (16px by default).
- Read the equivalent rem value; it also converts rem back to px.
The px to rem formula
rem = px ÷ root font size. With the default 16px root, 24px equals 1.5rem. Unlike em, rem always refers to the root font size, so it isn’t affected by parent elements.
Why rem is predictable
The big advantage of rem over em is that it never compounds. An em is relative to the current element’s font size, so nesting sized elements multiplies the effect and a value can drift unexpectedly deep in the tree. A rem is always measured from the single root font size, so 1.5rem is the same everywhere on the page. That predictability makes rem the safer default for font sizes, spacing, and layout dimensions.
Rem and accessibility
When a visitor increases their browser’s default text size, the root font size grows, and everything you sized in rem grows with it — text, padding, and even media-query breakpoints if you use rem there. Sizing in pixels ignores that preference and can leave text stuck small. A common, robust pattern is to leave the root at the browser default (usually 16px) and express the rest of your UI in rem, so the whole interface scales from one accessible setting.
Frequently Asked Questions
How do I convert px to rem?
Divide the pixel value by the root font size. At 16px, 24px is 1.5rem. The converter calculates it instantly in both directions.
What is the difference between rem and em?
Rem is always relative to the root font size, while em is relative to the element’s own or parent font size. Rem is more predictable for consistent scaling.
Why use rem for accessibility?
Because rem scales with the user’s root font-size preference, text and spacing respect a visitor’s browser settings, which improves accessibility.