PX / REM / EM Converter
Paste a length in px, rem, or em and see all three units at once, computed against a customizable base font size. Converted in your browser — never sent.
Developer notes
• Pure arithmetic — no color or unit library, unlike Color Converter's colorjs.io dependency. • rem and em share the same baseFontSize; this is a simplification, not a true per-element parent-context em. • px is always shown as an integer; precision only affects the rem/em decimal places. • A bare number with no unit suffix is treated as px. • The reference table's 25 px values are fixed in v1 and recompute live against baseFontSize/precision.
Options
- Base font size — The root font-size in px that rem and em are computed against. Recomputes the paste result and every reference-table row. Default 16 (the browser/CSS default).
- Precision — Decimal places shown on computed rem/em values, in both the paste result and the reference table. Does not apply to px, which is always an integer. Default 2.
- Reference table — Shows or hides the 25-row quick-reference table of common px values with live rem/em equivalents. Default on.
Related CSS tools
Hub: Color & CSS Tools. Convert colors with Color Converter, check contrast with Color Contrast Checker, or shrink and format stylesheets with Minify CSS and Beautify CSS.
PX / REM / EM Converter FAQ
Paste-local universal length converter
What length formats can I paste?
A px, rem, or em value, or a bare number (treated as px). No other CSS unit (%, vw, vh, pt, ch) is supported in v1.
How is em different from rem here?
It isn't — em shares the same customizable baseFontSize as rem, matching how most dedicated calculators simplify em. This is not a true per-element parent-context em.
Are my values uploaded anywhere?
No. Conversion is pure arithmetic that runs entirely in your browser. FastMinify never sends the pasted length to a server.
What does the reference table show?
A fixed set of 25 common px values (0 through 128, tracking the Tailwind spacing scale) with their live rem and em equivalents against your current base font size and precision.
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