CSS Units Converter
/css-units-converterConvert between px, rem, em, %, vw, and vh with a configurable base font size. Perfect for responsive design.
Responsive design means juggling px, rem, em, and vw values, which requires constant mental math. This converter translates values between CSS units using a configurable base font size. It is especially useful when porting a fixed-width layout to fluid units. Conversion happens instantly in your browser.
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FAQ
Frequently asked questions
Everything you need to know about css units converter.
Which units are supported?
Pixels, rem, em, percentages, vw, and vh are all supported, and you can convert any pair of them with instant results.
What base size is used for rem?
The default base is 16 pixels, the browser default, but you can change it to match your design system's root font size for accurate conversions.
Why does the base font size matter?
rem units are relative to the root element's font size, while em units are relative to the current element's font size, so the base value directly affects the pixel result.
Do vw and vh conversions need a viewport?
Yes. Set a reference viewport width and height to get accurate conversions, since vw and vh are percentages of the viewport size.
Is my data sent anywhere?
No. All unit conversions run entirely in your browser, so design values and base sizes never leave your device.
When should I use rem over px?
rem scales with the user's root font size, which improves accessibility for users who enlarge their default text, while px stays fixed regardless of preferences.
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