HTMLCSS Unit Converter
Convert CSS units: px to rem/em, vw to px, and more. Set your base font size once and convert any value instantly. Generates ready-to-paste CSS for responsive layouts.
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What base font size should I use?
Browsers default to 16px. If you haven't changed the root font-size in CSS, use 16 as your base for px↔rem conversions.
When should I use rem vs em?
rem is relative to the root element — predictable for global spacing. em is relative to the current element — useful for component-scoped sizing.