Converts a length between px, rem, em, pt, vw, vh, and percent all at once. Fast, free, and built for simple browser-based workflows.
Results update as you type. Click any value to copy it.
| Unit | Value | Notes |
|---|
728 x 90 In-Content Ad
CSS Unit Converter is a free online tool that converts a length between px, rem, em, pt, vw, vh, and percent at once. Enter a value and its unit, and every equivalent appears in a table you can click to copy -- no manual math or lookup table needed.
It is useful when a design file gives you a pixel measurement but your codebase is built on rem for accessibility, when you are translating a fixed layout into viewport units for responsive design, or when you need to know what percentage a font-size actually resolves to against its parent element. Setting a custom root and parent font size also matches results to a project that does not use the 16px browser default.
Everything runs inside your browser using formulas you can check line by line, so no measurement is sent to a server. Results update as you type, which makes it fast to try several root font sizes or viewport widths side by side without reloading anything.
Type a number into Value and choose its Unit, e.g. 16 and px.
Adjust Root Font Size, Parent Font Size, Viewport Width, and Viewport Height if your project does not use the 16px / 1920x1080 defaults.
All seven units update instantly as you type or change any setting.
Click any result in the table to copy it, complete with its unit. Reset restores the defaults.
Yes! All our tools are 100% free to use with no hidden costs, no registration required, and no credit card needed.
Absolutely. All tools run entirely in your browser (client-side). Your data never leaves your device and is not sent to our servers.
Yes, once the page is loaded, the tool will continue to work even if you lose internet connection since it runs in your browser.
There is no strict character limit, but very large amounts of text (100,000+ characters) may slow down your browser.
Yes! All our tools are free for both personal and commercial use.
rem units are always relative to the root (html) element's font size, which defaults to 16px in every browser but can be changed by a site's own CSS or a visitor's accessibility settings. Setting it here matches the conversion to your actual project instead of assuming the default.
em is relative to the font size of the element's own parent, so nested elements can compound; rem is always relative to the root element's font size, so it stays predictable no matter how deeply nested an element is. That is why the tool has separate root and parent font size fields.
Using the standard print-to-screen ratio of 96 pixels per inch and 72 points per inch, so 1pt equals 96/72, or about 1.333px. This is the same ratio browsers use internally.
vw and vh are percentages of the browser window's width and height, so the same value produces a different pixel result on a 1920px-wide screen than on a 375px-wide phone. Entering your actual target viewport gives an accurate conversion for that screen.
Yes. Enter a value in any of the seven supported units and the table shows its equivalent in all of the others at once -- there is no need to pick a "from" and "to" unit separately.
They use the same base but express it differently -- em shows a multiplier of the parent's font size (e.g. 1.5em), while % shows the same relationship as a percentage (e.g. 150%). The underlying pixel value is identical.