Meaning of font size

Question

What is font size in LaTeX? More precisely, What does LaTeX mean for 12 point? How space does get a letter in output of LaTeX's file in 12 pt?

\documentclass[12pt]{article}

Welcome to tex.sx. Your question is rather too vague: What do you want to know exactly? What do you already know about font size and point sizes, within or beyond the LaTeX context? Have you tried to google the question yourself, and what did you find that you don't understand? — alexis, Dec 07 '13 at 20:15
@Sigur In fact, that's not usually true. 1pt in TeX is 1/72.27 inches, whereas 1pt in Office is 1/72 inches, which TeX calls bp (big point). — Alan Munn, Dec 07 '13 at 20:21
Related questions: What point (pt) font size are \Large etc.? and What are the various units (ex, em, in, pt, bp, dd, pc) expressed in mm?. Perhaps this question is a duplicate of the first? — Alan Munn, Dec 07 '13 at 20:22
A better visual indicator of the "point size" of a font is the height of a round parenthesis, i.e., ( and ). In many font families the height of a parenthesis is very close to the nominal point size. — Mico, Dec 07 '13 at 20:51
@bigli yes, a em space is usually very close to width of a capital M. — Ray Tayek, Aug 16 '17 at 00:51

alexis · Answer 1 · 2013-12-08T12:22:47.590

4

These are general typographical conventions. One point is defined as 1/72.27 inches. Font sizes are traditionally identified by the width of the widest letter, M (other traditions base it on height), or more precisely by the dimensions of an abstract "em box" in which the font's letters are placed. (Hence, the actual width of M will be different.) An "em" is a font-dependent dimension that is (by definition) exactly equal to the width of the em box, so that in a 12 point font, 1em == 12pt.

In LaTeX, 12pt is actually the name of a document class option. Only 12pt, 11pt, and 10pt (the default) are defined as options for the standard LaTeX classes. These define the base font; section heads and footnotes use other, appropriate sizes.

edited Dec 08 '13 at 12:22

answered Dec 07 '13 at 20:17

alexis

7,961

If width of the letter M to be 12pt, how is it for otherwise? How is it for empty space between two words in 12pt ? – bigli Dec 07 '13 at 20:29
@bigli - the width of interword space is usually much less than that of M. – Mico Dec 07 '13 at 20:48
Interword spaces are flexible, to allow for text to be exactly aligned with both margins. The width of all letters depends on the font, and the distance may be adjusted for each pair of letters ("kerning"). – alexis Dec 07 '13 at 21:04
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The width of an M in cmr10 is 9.167pt. The width of M in cmbx10 is 10.9167pt. Knuth claims the point size of a font is the height of its parentheses. In my experience even this is not always true (except, perhaps, in the fonts Knuth created). – Dan Dec 07 '13 at 23:25

Meaning of font size

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