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I know there are different ways of expressing sizes or dimensions in LaTeX such as points (pt), inches (in) and ex.

As some commands, such as \hspace understand all of them, I would like to have a reference or complete list of possible dimensions or sizes including a description of what they mean.

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The definitive reference is the TeXbook by Donald Knuth; the source of which is freely available. –  Martin Schröder Jan 17 '12 at 16:59

1 Answer 1

up vote 38 down vote accepted

From the plain TeX reference:

  • pt: Point
  • pc: pica (12 pt)
  • in: inch (72.27 pt)
  • bp: Big point (72 bp = 1 in)
  • cm: Centimeter
  • mm: Millimeter
  • dd: Didot point
  • cc: cicero (12 dd)
  • sp: Scaled point (65536 sp = 1 pt), the smallest TeX unit
  • ex: Nominal x-height
  • em: Nominal m-width

Available in math mode:

  • mu: math unit, 1 em = 18 mu, where em is taken from the math symbols family, various lengths are derived from it (thinspace, thickspace, etc.)

Additionally available in pdfTeX and LuaTeX:

  • px: "pixel", the dimension given to the \pdfpxdimen primitive; default value is 1 bp, corresponding to a pixel density of 72 dpi

See also here on TeX.SX:

The meanings of the various points are described here:

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Thanks a lot. Could you expand a little on Didot points and the meaning of the nominal in ex and em? –  Henrik Jan 17 '12 at 14:34
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It is worth to note that "sp" is the smallest TeX unit and that it cannot be subdivided further. Thus any length in TeX is an integer multiple of "sp". –  AlexG Jan 17 '12 at 14:39
    
em: It is M-width –  Herbert Jan 17 '12 at 14:39
    
pdftex and luatex have also the px unit, whose value can be changed on a per document basis (default 1px = 1bp). –  egreg Jan 17 '12 at 14:41
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there's also the mu -- math unit (1 em = 18 mu, where em is taken from the math symbols family). this can be used only in math mode. –  barbara beeton Jan 17 '12 at 14:49

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