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, with 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
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 different here. em shares the same customizable baseFontSize as rem, which is 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?
It lists 25 common px values from 0 to 128, following the Tailwind spacing scale. The rem and em equivalents update live with your base font size and precision.
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