Why does rem conversion depend on the base font size?

rem is relative to the root element's font size. Change the base font size field to match your CSS :root or html font-size.

What is the difference between em and rem?

em is relative to the parent element's font size, while rem is always relative to the root font size. This tool uses the base font size for both as a reference point.

How are vw and vh calculated?

1 vw equals 1% of the viewport width and 1 vh equals 1% of the viewport height. Adjust the viewport dimensions fields to match your target screen.

Is pt the same as px?

No — 1 pt equals 1/72 of an inch (approximately 1.333 px at 96 dpi). Points are mainly used in print stylesheets.

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CSS Unit Converter

Convert a CSS value between px, rem, em, %, vw, vh, pt, cm, mm, and in all at once.

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About this tool

Enter a value in any CSS unit and immediately see its equivalent in every other unit. Configure the base font size, viewport width, and viewport height so the conversions match your actual project. A handy reference table of common responsive breakpoints in all units is included at the bottom.

How to use

1 Step 1: Set your base font size (default 16 px), viewport width, and viewport height at the top.
2 Step 2: Enter a value in any unit field — all other fields update instantly.
3 Step 3: Read the conversion table to find the equivalent in the unit you need.
4 Step 4: Scroll down to the breakpoint reference for commonly used responsive design values.

About this tool

How to use

Frequently Asked Questions