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CSS Unit Converter

Turn design-spec pixels into rem, em, and viewport units in this tab — and see print-unit equivalents side by side.

Processed in your browser

Conversion runs in this browser. We do not send values.
CSS unit conversion finishes in this browser. Values stay on this device and are not uploaded.

Any finite number; decimals allowed.

The CSS unit that value is currently in.

Used for rem; commonly 16.

Used for em.

Used for percent.

Used for vw.

Used for vh.

Enter a value and unit, then convert.

Features

Common relative units

Convert px, rem, em, %, vw, and vh together.

Configurable context

Tune root font, parent font, parent width, and viewport.

Print unit reference

Show pt, cm, mm, and in at the CSS 96ppi reference.

Stays in the browser

Math runs on this device. Values are not uploaded.

How to use

  1. Enter a number and choose its source unit (for example 16 and px).
  2. Set root font size, parent font size, parent width, and viewport as needed.
  3. Press Convert, then copy the rem, em, vw, or other result you need.

Why this tool

Runs in the browser

Core work finishes in this tab.

No upload

Pasted text and local files are not sent away for processing.

Free, no account

The core path has no signup wall.

Immediate

There is no upload-and-wait queue.

10 languages

The same tool ships in ten languages.

Readable failures

Broken input returns a reason, not a blank screen.

FAQ

Are values uploaded?
No. Conversion runs in this browser. Values are not sent.
What is the difference between rem and em?
rem is relative to the root font size; em is relative to the parent font size. Set both in the context fields.
How are vw and vh calculated?
1vw is 1% of the viewport width; 1vh is 1% of the viewport height. Enter the target viewport size.
Is it free? Do I need an account?
Yes, it is free. No account is required to convert or copy.

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