# Document margins with a4paper: documentclass vs. geometry [duplicate]

Using pdflatex, I would like to set an A4 article. I believed (from this answer) that it did not matter whether I use

\documentclass[a4paper]{article}


or

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


But when I compile the two, I get different page margins. So I am now confused which is the "correct" way to use A4 paper. Is it maybe that one option only changes the paper format from letter to A4 but maintains the page margins, while the other adapts the margins to the new format? (Just a guess...)

MWE:

\documentclass{article}
\usepackage[a4paper]{geometry} %\documentclass[a4paper]{article} as the alternative
\begin{document}
Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Aliquet risus feugiat in ante metus dictum. Auctor urna nunc id cursus metus aliquam. Malesuada proin libero nunc consequat interdum varius sit amet mattis. Quis ipsum suspendisse ultrices gravida dictum fusce ut placerat orci. Pellentesque habitant morbi tristique senectus et netus et. Quam viverra orci sagittis eu volutpat odio. Tellus id interdum velit laoreet id donec ultrices. Ut lectus arcu bibendum at. In aliquam sem fringilla ut. Tristique senectus et netus et malesuada. Semper eget duis at tellus at. Tincidunt lobortis feugiat vivamus at. Volutpat commodo sed egestas egestas fringilla. Lorem mollis aliquam ut porttitor. Vitae auctor eu augue ut lectus.
\end{document}


## marked as duplicate by Bernd, Mensch, Raaja, Stefan Pinnow, ZarkoJun 24 at 10:02

• @Daniel: You are just right, it seems! The default \textwidth of the letter format is apparently 345pt, which is maintained if I set the page size via the documentclass option. If I use the geometry package instead, it is changed to approx. 418.25. Thanks for the hint! – Bernd Dec 22 '18 at 11:01
• It depends :-) The real question is what is a "correct" margin and if you consider the text area or the margin or the proportion between both as the defining characteristic of "correctness". IMHO, the standard LaTeX classes are letter-centric, so geometry may have the better defaults for A4. I personally prefer koma-script and its typearea package, which calculates the margin depending on typographic rules. Its documentation, Chapter 2, provides a good introduction into the topic of typographic page calculations, definitely worth a read. – Daniel Dec 23 '18 at 23:36