Margin differences in class a4paper and geometry a4paper

Question

I am currently writing a paper whose class settings are the following.

\documentclass[12pt, a4paper]{report}

Soon I will need to print it as a twoside document. When I add the twoside option the entire document is affected including the "cover page". If I am not mistaken the only easy way to make the document a two side one without affecting the cover page is by using the geometry package and then by adding \newgeometry{twoside} after the cover page. Unfortunately geometry package modify the margins of the document. I prefer the default ones for a4paper so I tried to change them by means of the following options.

\usepackage[a4paper, centering, total={5.4in, 8.18in}, twoside, bindingoffset=1cm]{geometry}

What are the precise dimensions of the margins for an a4paper, report document without geometry? I derived 5.4in, 8.18in approximately by trial and error but they are not correct.

EDIT

First picture no geometry package, a4paper. Second picture geometry package, a4paper.

Answer 1

What are the precise dimensions of the margins for an a4paper, report document without geometry?

They are in columns two and three of the table for oneside and twoside. (the 62pt allocated to the margins are split in a different way). The code shows how to get this values.

But, more important, you also wanted to keep the original layout of the cover while changing the document to twoside. As you suggested it can be done with the package geometry, loaded with appropriate parameters for report oneside and then recover the twoside with \newgeometry.

Test to be done with the code provided:

(1) Use \documentclass[12pt,a4paper]{report} and comment both \usepackage[...]{geometry} and \newgeometry[...] (placed before \chapter).

You should get the values of the second column of the table (report oneside), both in "Geometry of the title page" and in "Geometry of the document".

(2) Now use \documentclass[12pt,a4paper, twoside]{report} keeping the two lines commented. You will get the values of the third column, report twoside, both for the cover and the rest of the document.

This is something undesirable because it changes the layout of the cover.

(3) Un-comment only \usepackage[...]{geometry}. You recover the values of oneside for everything. Fourth column of the table. One more step to go.

(4) Un-comment also \newgeometry[...] placed before \chapter. Now you will get the the values for report twoside in "Geometry of the document" (fifth column) while keeping the oneside values for "Geometry of the title page" (fourth column). The desired result.

This is the code

%\documentclass[12pt,a4paper]{report} % used to write the document 

\documentclass[12pt,a4paper,twoside]{report} % required to print the document

\usepackage[textwidth= 390.0pt,
textheight =592.0pt,
left= 103.27pt,  % 1in + 31pt
top= 92.27pt, % 1in + 20pt
marginparwidth= 85pt,
includemp,
includehead]{geometry} % reproduce report oneside layout

\title{Draft title of the report}
\author{Only one}

\begin{document}
    
\setlength{\parindent}{0pt} 

\textbf{\large Geometry of the title page}
\medskip

textwidth=  \the\textwidth

textheight= \the\textheight

oddsidemargin= \the\oddsidemargin

evensidemargin= \the\evensidemargin

topmargin= \the\topmargin

headheight= \the\headheight

headsep= \the\headsep

topskip= \the\topskip

footskip= \the\footskip

marginparwidth= \the\marginparwidth

marginparsep= \the\marginparsep
    
\maketitle

\newgeometry{twoside,  % recover report twoside layout
    textwidth= 390.0pt,
    textheight= 592.0pt,
    left= 82.27pt,  % 1in + 10pt
    top= 92.27pt, % 1in + 20pt
    marginparwidth= 85pt,
    includemp,
    includehead}    

\chapter{Measurements}

\textbf{\large Geometry of the document}
\medskip

\setlength{\parindent}{0pt} 

textwidth=  \the\textwidth
    
textheight= \the\textheight

oddsidemargin= \the\oddsidemargin

evensidemargin= \the\evensidemargin

topmargin= \the\topmargin

headheight= \the\headheight
 
headsep= \the\headsep

topskip= \the\topskip

footskip= \the\footskip

marginparwidth= \the\marginparwidth

marginparsep= \the\marginparsep

\bigskip
\begin{tabular}{lcccc}
    \hline
                   &   report 1s   &   report 2s   & geometry \& 2s & +newgeometry \& 2s \\
                   & cover + pages & cover + pages & cover + pages  &     only pages     \\ \hline
    textwidth      &    390.0pt    &    390.0pt    &    390.0pt     &      390.0pt       \\
    textheight     &    592.0pt    &    592.0pt    &    592.0pt     &      592.0pt       \\
    oddsidemargin  &    31.0pt     &    10.0pt     &     31.0pt     &       10.0pt       \\
    evensidemargin &    31.0pt     &    52.0pt     &    31.97pt     &      52.97pt       \\
    topmargin      &    20.0pt     &    20.0pt     &     20.0pt     &       20.0pt       \\
    headheight     &    12.0pt     &    12.0pt     &     12.0pt     &       12.0pt       \\
    headsep        &    25.0pt     &    25.0pt     &     25.0pt     &       25.0pt       \\
    topskip        &    12.0pt     &    12.0pt     &     12.0pt     &       12.0pt       \\
    footskip       &    30.0pt     &    30.0pt     &     30.0pt     &       30.0pt       \\
    marginparwidth &    85.0pt     &    85.0pt     &     85.0pt     &       85.0pt       \\
    marginparsep   &    10.0pt     &    10.0pt     &     10.0pt     &       10.0pt       \\ \hline
\end{tabular}
    
\end{document}

Answer 2

I have answered this before somewhere but I couldn't find the duplicate so ...

The two options are doing very different things.

Classically TeX has no concept of paper size or margin, it just sets the size of the text block and the margins are the difference between that and whatever size paper you print on.

There is a nominal offset of 1in from the top left corner but that was typically adjusted in the dvi driver rather than in TeX, and there are no TeX primitives corresponding to the right margin at all.

Most dvi drivers (and tex variants with a built in back end such as pdftex and luatex) have a way of specifying the media size that can be used to set the page dimensions in PDF.

At the time LaTeX2e was designed pdflatex was very new and almost all tex use was via classic dvi tex with a multitude of dvi drivers so by default latex makes no assumptions about the back end in use.

So a4paper option in the standard classes sets a text block suitable for A4, and sets the latex \paperwidth and \paperheight dimension registers to the size of A4. But it does not set any dvi driver \special nor the pdflatex primitives \pdfpagewidth and \pdfpageheight to actually force the PDF to be A4. The PDF page dimension will be set typically by an installation default when you installed texlive, which might be US Letter size.

Packages such as geometry, graphicx, hyperref which do determine the back end system in use all normalize the settings so that \pdfpagewidth, \pdfpageheight or equivalent specials or luatex primitives are set based on the values of \paperwidth and \paperheight, thus forcing the dimension of the PDF page to match the latex specified paper size. So even if you use no options at all, the margins, espically the implicit right and bottom margins, may change.

Answer 3

You can use the layouts package to report the current page layout values (and also see what happens if you change them). You can use the changepage package's adjustwidth environment to temporarily alter the current left and right margins. Here is an example.

% marginsprob.tex  SE 591067
\documentclass[12pt, a4paper]{report}
\usepackage{layouts}
\usepackage{changepage}
\usepackage{lipsum}

\begin{document}

% The current page layout lengths
\begin{figure}
\currentpage
\pagedesign
\caption{This page layout values}
\end{figure}

% The general page layout length commands
\begin{figure}
\pagediagram
\caption{Page layout parameters}
\end{figure}
\clearpage

\lipsum[1]

\begin{adjustwidth}{-1cm}{1cm}
 \textbf{Adjusted} \lipsum[2]
\end{adjustwidth}

\lipsum[3]

\end{document}

I suggest you use layouts to find what the dimensions of a4paper and a4paper,twoside are. Then use \documentclass[12pt,a4paper,twoside]{report} but use adjustwidth environment for the first title page followed by a move to the remainder of the document.