Difference between DIV=calc and default DIV for Koma Script class scrbook

Question

I find strange in the example bellow that when I activate the option DIV=calc for the document class scrbook the calculated DIV value for the document becomes different than the predifined values in Table2.2 of the Koma Script manual.

Normaly, the DIV=calc option is supposed to optimize the DIV value for a given paper and font size.

In the following example, A4 paper is selected without specifying a font size. Therfore, logically the calculated DIV value must be the same as the predifined one, or not ?

First example

\documentclass[paper=a4,twoside,BCOR=2.5mm,DIV=calc]{scrbook}

\begin{document}

\makeatletter Koma has selected the following DIV value: $$DIV = \the\ta@div$$ and the following BCOR value $$BCOR = \the\ta@bcor$$ \makeatother

\end{document}

and when removing the option DIV=calc :

Answer 1

All KOMA-Script classes use DIV=default by default. The symbolic value default means: Calculate type area using the standard value for the current page format and current font size. If no standard value exists, calc is used.

The standard DIV values can be find in a table in the documentation:

• paper=a4 and fontsize=10pt -> standard DIV value: 8
• paper=a4 and fontsize=11pt -> standard DIV value: 10
• paper=a4 and fontsize=12pt -> standard DIV value: 12

In your example there is paper=a4, fontsize=11pt (default), so DIV=default results in DIV=10.

The standard values does not take the used font into account. But you will get a warning by package typearea if there are clearly too many or too few characters in a normal text line.

With DIV=calc takes the chosen font and its characteristics (width of the characters etc.) into account.

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Update

There was a bug in typearea: until (including) version 3.24 the standard DIV values for fontsizes 10pt (DIV=8), 11pt (DIV=10) and 12pt (DIV=12) were used even if the paper format was not A4. This bug will be fixed in version 3.25. So if you use a version before 3.25 and not the default paper=a4 Option then an explicit DIV=calc is recommended.