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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. Commented Jan 17, 2012 at 16:59

2 Answers 2

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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 (1157 dd = 1238 pt)
  • 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
    Commented Jan 17, 2012 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
    Commented Jan 17, 2012 at 14:39
  • em: It is M-width
    – user2478
    Commented Jan 17, 2012 at 14:39
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    pdftex and luatex have also the px unit, whose value can be changed on a per document basis (default 1px = 1bp).
    – egreg
    Commented Jan 17, 2012 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. Commented Jan 17, 2012 at 14:49
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I made visual overview for all units available in TeX. Including a comparison and the definitions/conversions.

previwe

The complete code and PDFs (EN, DE; b/w, color) are available at GitHub: https://github.com/tweh/tex-units

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  • Oh my.... (+1) Some people do have too much time :D
    – user31729
    Commented May 23, 2016 at 15:36
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    @ChristianHupfer: Actually too much work to not procrastinate ;-)
    – Tobi
    Commented May 23, 2016 at 15:39
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    I believe you have mislabeled the PostScript point: tex.stackexchange.com/questions/21758/…
    – Alan
    Commented Jul 3, 2016 at 20:29
  • @Alan: Indeed … thanks! Don’t know where this mistake came from …
    – Tobi
    Commented Jul 3, 2016 at 20:44
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    Amazing. The github source has a PDF version. Super useful, thanks!
    – PatrickT
    Commented Feb 8, 2021 at 10:17

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