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If no changes has been made to the settings of indentation of an article class LaTeX document, what is the width of the paragraph indent?

texdoc article in the terminal opens the Standard Document Classes for LaTeX version 2e manual. In section 6.2 Paragraphing I find the following line:

⟨10pt⟩ \setlength\parindent{15\p@}

The \p@ means 1pt ... so I guess this would mean that the standard indent is 15 pt at a 10 pt text size? Is this correct?

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PetaspeedBeaver
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    Correct you can also do \the\parindent to print it in a minimal or \showthe\parindent to see it on the terminal – yannisl May 28 '15 at 12:33
  • Could you please elaborate a bit on how to use the commands you wrote? I'm quite new to LaTeX. – PetaspeedBeaver May 28 '15 at 12:47
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    If you insert @YiannisLazarides' macros in your document .tex file, the first will list the indent directly in your output document, while the second will list it in the log file. Also, if you want a responding comment on this site to be brought to the attention of the person, you need to insert @ followed by the recipient name in your comment (as I have done above). Welcome to the site. – Steven B. Segletes May 28 '15 at 12:56
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    @StevenB.Segletes Ah, I understand! – PetaspeedBeaver May 28 '15 at 13:22
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    Also: if you just open a terminal and type tex (or latex), then hit return, you're given an interactive prompt where you could then type \showthe\parindent, hit return, and then get the output: > 20 pt. Then type x and return to exit. – jon May 28 '15 at 15:23

1 Answers1

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The standard classes article and report use sizeXY.clo to set parameters for the XYpt option, that is 10pt (default), 11pt and 12pt.

In size10.clo we find

\if@twocolumn
  \setlength\parindent{1em}
\else
  \setlength\parindent{15\p@}
\fi

which means that the parindent is different in twocolumn mode than in one column typesetting. The command \p@ stands for a dimension register storing the value 1pt, so 15\p@ is equivalent to 15pt. In size11.clo there is

\if@twocolumn
  \setlength\parindent{1em}
\else
  \setlength\parindent{17\p@}
\fi

and in size12.clo there is

\if@twocolumn
  \setlength\parindent{1em}
\else
  \setlength\parindent{1.5em}
\fi

The same values are found in bk10.clo, bk11.clo and bk12.clo that are used by the book class.

Note that these values are set after a \normalsize declaration, but before \normalfont is issued, so the value of em is the one relative to the corresponding font in the Computer Modern family.

If you want to set a value of \parindent in em units relative to the document font, do

\AtBeginDocument{\setlength{\parindent}{1em}}

(or whatever value you prefer).

egreg
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  • Equivalently, one could use latexdef or texdef command, for example latexdef -c '[10pt]{article}' -v parindent will return 15.0pt; and latexdef -c '[11pt]{article}' -v parindent will return 17.0pt. – Quar Feb 14 '21 at 19:36