Consider this example:
\documentclass{report}
%% \clubpenalty=10000
%% \widowpenalty=10000
\begin{document}
\tableofcontents
\chapter{Introduction}
\chapter{Background}
\chapter{Setup}
\chapter{Methodology}
\chapter{Data}
\chapter{Statistical Selection}
\chapter{Uncertainties}
\chapter{Results}
\section{Results of methodology 1}
\section{Results of methodology 2}
\section{Results of methodology 3}
\section{Results of methodology 4}
\section{Results of methodology 5}
\section{Resuts of methodology 6}
\section{Results of methodology 7}
\section{Results of methodology 8}
\section{Results of methodology 9}
\section{Results of methodology 10}
\section{Results of methodology 11}
\section{Results of methodology 12}
\section{Results of methodology 13}
\section{Results of methodology 14}
\section{Resullts of methodology 15}
\chapter{Conclusions}
\chapter{Appendix}
\chapter{Bibliography}
\end{document}
The TOC continues to next page with only one line:
There is no improvement also after I uncomment the lines:
%% \clubpenalty=10000
%% \widowpenalty=10000
which I tried according to How do I prevent widow/orphan lines?
How to make TOC either more sparse so that page 2 has more lines or more compact so that TOC is not continued to page 2?




;-)Don't worry about this until the document is finished. At that point, just after\begin{document}add\addtocontents{toc}{\protect\enlargethispage*{\baselineskip}}and rerun LaTeX a couple of times. You might need2\baselineskipor even-2\baselineskipdepending on how many lines actually end up in the second page. – egreg Apr 16 '19 at 16:24