CSS Unit Converter helps frontend developers translate common CSS units for responsive layout work. It is useful for checking spacing, typography, and viewport-based sizing without manual math.
Yes. The tool is free and runs directly in your browser with no account required.
No. All conversion happens locally in the browser tab. Nothing is sent to a server.
px, rem, em, %, vh, vw, pt, cm, mm, and in. Enter a value in any one unit and see the equivalent value in all the others simultaneously.
rem is calculated against the 'Base font size' field (the root element's font size), while em and percent are calculated against the separate 'Parent element' field, matching how they actually cascade in CSS.
Using the 'Viewport width' and 'Viewport height' fields you set, so you can check how a viewport-relative value would render at a specific screen size (e.g. 1440x900 for desktop or 375x812 for mobile).
Using rem units for font sizes and spacing lets values scale when a user changes their browser's default font size, which is a common accessibility and responsive design practice.
They're converted using the CSS specification's fixed reference (96px = 1 inch), which is standard for print stylesheets but won't exactly match physical size on every screen due to differing pixel densities.
