= Point
{disambiguate=typography}
{title2=$\mathrm{pt}$}
{wiki}
= Typographic point
{synonym}
A <typographic point> is a unit used for <font size>, <line height> and other typographic distances. In the modern digital convention,
$$
\boxed{1\,\mathrm{pt}=\frac1{72}\,\mathrm{in}
=\frac{127}{360}\,\mathrm{mm}\approx0.352778\,\mathrm{mm}.}
$$
Here the <inch> is 25.4 <millimetres>. The equation describes the digital convention; historical typographic point systems have not all used that same length. The modern `pt` relation also appears among the absolute-length units defined for <CSS>.<CSS Values and Units Module Level 3 by World Wide Web Consortium>[Section5.2: absolute lengths and the pt, in and px equivalences]{ref}
For example, a <font size> of 12 <typographic points> corresponds to a nominal <em> of one sixth of an <inch>, approximately 4.2333 <millimetres>. That sets the outline's scale, rather than the exact ink height of every <glyph>. A particular <x-height> or <glyph advance> can be a different fraction of an <em>.
The <CSS> conversion also gives 12 <typographic points> as 16 <CSS pixels>. A <CSS pixel> is a layout unit, so this equality does not promise 16 hardware <pixels> or a ruler-measured physical height on every screen. Zoom and the mapping to device <pixels> must be accounted for separately; the <device pixel ratio> records one part of that mapping.
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