Typography

Em

Definition

The em is a relative typographic unit equal to the current element's font size; in a 16 px context, 1 em equals 16 px.

Explanation

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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RELATED CONVERSIONS

Em → Pixel Em → Point Em → Pica Em → Rem Em → Inch (CSS) Em → Centimeter (CSS)
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RELATED ARTICLES

Typography Units: Points, Pixels, Ems, and Picas

A complete guide to typography units — from Gutenberg-era points and picas to CSS pixels, ems, and rems for modern digital design.
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RELATED TERMS

Pica

The pica is a typographic unit equal to 12 points or exactly 1/6 of an inch (approximately 4.233 mm), used primarily to measure column widths and other layout dimensions.

Twip

A twip (twentieth of a point) is a typographic unit equal to 1/20 of a printer's point, or 1/1440 of an inch (approximately 17.64 micrometers).

Cap Height

Cap height is the typographic measurement of the height of a flat uppercase letter (such as 'H' or 'I') from the baseline to the top of the letter, expressed as a fraction of the font's em square.

X-Height

X-height is the typographic height of a typeface's lowercase letters, specifically the height of a flat lowercase 'x' measured from the baseline, typically expressed as a fraction of the em size.