CSS Unit Converter (px, em, rem, pt)

Utilities Free Updated 4 Oct 2026

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ⓘ About this tool 🔄 Last updated 4 Oct 2026 ✓ Reviewed by TopToolAI Team

Converts a CSS size between pixels, em, rem, and points, using the root font size you specify (16px is the common browser default).

How to use CSS Unit Converter (px, em, rem, pt)

Step-by-step guide to the boxes below. Open it only if you need help.

1

Value Text

The number you want to convert.

Example: 16
2

From unit Choose one

The unit your number is in now.

Choose one: pxemrempt
3

Root font size (px) Text

Browser default is 16px unless your CSS changes it.

Example: 16
4

Press “Convert”

Click the button under the boxes. If something is missing or not valid, a short message tells you which box to fix.
5

Read your result

Your answer appears under the button, with a short note in plain words where it helps. Change any box and press again to compare different numbers.

Go to the calculator

Embed this calculator on your website

Want this calculator on your own site? Copy the code below and paste it into the HTML of any page or post. It works the same as it does here. If you do not mind, leave the small link under it in place.

<iframe src="https://toptoolai.net/tool/css-unit-converter-px-em-rem-pt/?tw_embed=1" title="CSS Unit Converter (px, em, rem, pt)" width="100%" height="620" style="border:0;max-width:680px;" loading="lazy"></iframe>
<p style="font-size:12px;">Free <a href="https://toptoolai.net/tool/css-unit-converter-px-em-rem-pt/">CSS Unit Converter (px, em, rem, pt)</a> by toptoolai.net</p>

CSS Unit Converter (px, em, rem, pt) FAQs

What is the difference between em and rem?

em is relative to the font size of its parent element; rem is relative to the root (html) element's font size. This tool assumes a single base size for both, for simplicity.

What is a root font size?

The font size of the html element, usually 16 px. rem units are multiples of it.

When should I use px, em or rem?

px for fixed sizes like borders, rem for consistent, accessible text sizing, and em for sizes relative to the parent.

How do I convert px to rem?

Divide the pixel value by the root font size. 24 px with a 16 px root is 1.5 rem.

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CSS Unit Converter (px, em, rem, pt)

How to use CSS Unit Converter (px, em, rem, pt)

CSS Unit Converter (px, em, rem, pt) FAQs

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