Typography

Cadratin (em)

Définition

Le cadratin (em) est une unité typographique relative égale à la taille de police de l'élément courant ; dans un contexte de 16 px, 1 em équivaut à 16 px.

Explication

Historically, the em was the width of the uppercase letter 'M' in a given typeface — since 'M' was typically as wide as it was tall, it approximated the point size. In modern CSS and digital typography, em is purely relative to font-size, making it useful for scalable layouts: setting padding to 1 em ensures it always scales proportionally with text. The related 'rem' unit is relative to the root element's font size instead.

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