Convert between pixel, rem, and em units — set your base and convert instantly.
The quick brown fox jumps over the lazy dog
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PX to REM / EM Converter is a free online tool that converts between PX, REM, and EM CSS units instantly. Enter any pixel value and get the equivalent REM and EM values based on your base font size, with a complete reference table for quick lookups. Understanding CSS units is essential for responsive web design. PX (pixels) are absolute units, while REM and EM are relative units that scale with the user's font size settings. Using relative units improves accessibility and makes your layouts more flexible across different devices and user preferences. REM units are relative to the root element's font size (usually 16px by default), making them predictable and consistent across your entire stylesheet. EM units are relative to the parent element's font size, which can compound in nested elements. Knowing when to use each is key to maintainable CSS. Everything runs entirely in your browser. There are no usage limits and no account required. Common use cases include converting design mockups from pixels to relative units, building responsive typography scales, creating consistent spacing systems, migrating legacy CSS from pixels to modern relative units, and calculating media query breakpoints.