How to express 72.27pt in terms of \oddsidemargin, \textwidth, … that are subtracted from \paperwidth?

Question

By default, LaTeX appends one inch (72.27pt) to the left (and top) of document. Here I want to prove it as follows. But I missed some other page layout macros to subtract from \paperwidth.

% the objective is to prove that
% left padding of 1in  = 72.27pt
% has been added by default
% by LaTeX

\documentclass{article}

\begin{document}
    \the
    \dimexpr
        \paperwidth
        -\hoffset
        -\oddsidemargin
        -\textwidth
        -\marginparsep
        -\marginparwidth
        % minus some other page layout macros 
        % should be there but I don't know
    \relax
\end{document}

How to express 72.27pt in terms of \oddsidemargin, \textwidth, ... that are subtracted from \paperwidth?

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I need a length macro for the red segment below.

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The reason I accepted egreg answer is due to his comment below.

Again: the length you display in red is not available directly, but only through computation: it's \paperwidth-1in-\hoffset-\oddsidemargin-\textwidth-\marginparsep-\marginparwidth

Thus it is impossible to get the required expression to prove 72.27pt.

Answer 1

The upper left corner of the text block is placed

1in + \hoffset + \oddsidemargin

from the left border of the page and

1in + \voffset + \topmargin + \headheight + \headsep

from the upper border. Of course \evensidemargin is used when the page is considered to be a right page (only in twosided printing and when the page number is even).

You can "prove" what you want with the following example:

\documentclass[a4paper]{article}
\usepackage{layout}

\addtolength{\marginparwidth}{\dimexpr\paperwidth-1in-\hoffset-\oddsidemargin-\textwidth-\marginparsep-\marginparwidth-1pt\relax}

\begin{document}
\layout
\end{document}

Now the box representing the margin note area will extend just a bit short of the right edge of the paper (1pt, actually, but the image is not perfect because the lines have a thickness).

The length you draw in red is exactly

\paperwidth-1in-\hoffset-\oddsidemargin-\textwidth-\marginparsep-\marginparwidth

If all you need is a nonstandard page size with zero margins, the answer is geometry:

\documentclass{article}
\usepackage[paperwidth=1in,paperheight=1in,margin=0pt]{geometry}

The calculations performed by the package are summarized in the log file:

* paper: custom
* layout: <same size as paper>
* layoutoffset:(h,v)=(0.0pt,0.0pt)
* modes: 
* h-part:(L,W,R)=(0.0pt, 72.26999pt, 0.0pt)
* v-part:(T,H,B)=(0.0pt, 72.26999pt, 0.0pt)
* \paperwidth=72.26999pt
* \paperheight=72.26999pt
* \textwidth=72.26999pt
* \textheight=72.26999pt
* \oddsidemargin=-72.26999pt
* \evensidemargin=-72.26999pt
* \topmargin=-109.26999pt

Note that 72.27pt is the same as 72.26999pt, as far as TeX is concerned.