The width for the section numbers in the ToC is defined by the length called \cftKnumwidth
, where K
should be replaced by the sectioning level, i.e. chapter
, section
, etc. You can change it with \setlength
, e.g.
\setlength\cftsectionnumwidth{4em}
See section 9.2.2 Typesetting the entries of the memoir
manual for more on this.
A complete example:
\documentclass{memoir}
% \setlength\cftsectionnumwidth{4em} % uncomment to see difference
\begin{document}
\tableofcontents
\chapter{A chapter}
\setcounter{section}{999} % just for this example
\section{A section}
\end{document}
Or if you are using the book class, as per https://tex.stackexchange.com/a/336618/50702 and Torbjørn T.'s comment below:
\documentclass{book}
% note you need the subfigure option if you are using the subfigure package
%\usepackage[subfigure]{tocloft}
\usepackage{tocloft}
\setlength\cftsecnumwidth{4em}
\begin{document}
\tableofcontents
\chapter{A chapter}
\setcounter{section}{999}
\section{A section}
\end{document}