CSS Unit Converter

Convert CSS measurement values between px, rem, em, %, and viewport units with custom root font size.

How It Works & Processing Standards

Convert CSS measurement values between px, rem, em, %, and viewport units with custom root font size.

Your input data is never sent to any server and is securely processed on your device.

Current Limits

  • Maximum input length: 100,000 characters

CSS Unit Converter is a 100% free, browser-based online utility. All calculations and file conversions run locally inside your browser (Local-First) without sending data to remote servers, keeping your documents and inputs strictly private.

How to Use CSS Unit Converter

  1. 1
    Input Length ValueType the numeric value requiring conversion.
  2. 2
    Select UnitsChoose source unit (e.g. px) and target unit (e.g. rem).
  3. 3
    Set Root Font SizeSpecify base html font size (default 16px).

Common Use Cases

  • Translating Figma pixel designs into responsive rem units, auditing accessibility font sizes, and layout coding
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