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PX to REM Converter

CSS pixels to rem, em, pt and percent, both ways.

Tech Calculators Free, no sign-up Runs in your browser

The browser default is 16px. Change it only if your CSS does.

For the em figure.

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In rem
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In px
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In em
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In points
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As a percentage
pxremempt
rem is relative to the root element, em to the parent. Using rem for type and spacing means a user who raises their browser font size scales the whole layout, which is why it is the accessible default -- a px value ignores that setting entirely.

About the PX to REM Converter

PX to REM Converter moves a CSS value between pixels and rem, and shows em, points and a percentage alongside. The root font size is an input because rem is defined against it: 24px is 1.5rem when the root is the browser default of 16px, but 2.4rem if a stylesheet has set the root to 10px.

The difference between rem and em is which element they look at. rem is always relative to the root, so it gives the same length anywhere in the document. em is relative to the parent's font size, so it compounds: a 0.9em inside a 0.9em is 0.81 of the grandparent. That compounding is occasionally useful for component-local spacing and is usually a source of bugs, which is why rem is the safer default and the parent size is a separate box here.

The accessibility case for rem is the real reason to convert at all. A length in px ignores the font size a user has chosen in their browser settings; a length in rem scales with it. For anyone who has raised that setting -- and many people have -- the same page in rem stays usable while the same page in px stays small.

The page shows its working, not just its answer. Where there is a formula it is printed with your own numbers substituted in, so you can check the result rather than take it on trust -- which is the difference between a calculator you can use for something that matters and one you cannot.

Everything runs inside your browser. What you type is never uploaded, never logged and never stored, and the calculator keeps working if your connection drops after the page has loaded.

How to use the PX to REM Converter

  1. Choose convertThe fields below change to match what you pick, so only the figures that matter to your case are asked for.
  2. Enter value, root font size (px) and parent font size (px)Decimals are fine, and thousands separators are accepted and ignored.
  3. Read the in rem, in px and in emThe figures update as you type. The Calculate button is there if you would rather press something, but nothing waits for it.
  4. Copy or check the resultCopy the summary with the copy button, or open the table to check it row by row.

Features

  • Shows in rem, in px, in em, in points and as a percentage together, so you are not running it twice
  • A results table you can read across
  • Updates as you type, with no button to press and no page reload
  • Copy the result in one click
  • Free, no sign-up, and it runs entirely in your browser

Who uses this tool

The px to rem converter is used by writers, developers, students, marketers and anyone else who needs the job done once without installing software. Common cases include:

  • Converting a design handed over in pixels into rem for CSS
  • Building a type scale in rem from pixel values
  • Checking what a rem value renders as on a 10px root
  • Converting pixels to points for print styles

Frequently asked questions

What is the default root font size?

16px in every major browser, unless the user has changed it or your CSS overrides the html element.

Should I use rem or em?

rem for type, spacing and layout, because it does not compound. em is occasionally useful for spacing that should scale with a component's own font size.

Why does the 62.5% trick exist?

Setting the root to 62.5% makes it 10px, so 1.4rem is 14px and the mental arithmetic is easier. Enter 10 as the root size to see that scale.

How do points relate to pixels?

In CSS, 1pt is 1/72 inch and 1px is 1/96 inch, so a point is exactly 1.333 pixels and a pixel is 0.75 points.

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Checked and rebuilt on 2026-10-14. The method this calculator uses is described in the section above, and corrections go through the contact page.