I would like to know how to change the font size in the table of contents. Maybe make it 14pt or 16pt.

\documentclass[12pt]{report}
\begin{document}
\tableofcontents

\end{document}


You can use the tocloft package and the command families \cftXfont (for the sectional number and titles) and \cftXpagefont (for the page numbers):

\documentclass[12pt]{report}
\usepackage{tocloft}

\renewcommand\cftchapfont{\LARGE\bfseries}
\renewcommand\cftsecfont{\LARGE}

\renewcommand\cftchappagefont{\LARGE\bfseries}
\renewcommand\cftsecpagefont{\LARGE}

\begin{document}

\tableofcontents

Some text in standard size just for comparison.

\end{document}


Instead of \LARGE you can use any other font size switch or \fontsize{...}{...}\selectfont.

Redefining also the family \cftXafterpnum will give you better spacing between entries:

\documentclass[12pt]{report}
\usepackage{tocloft}

\renewcommand\cftchapfont{\LARGE\bfseries}
\renewcommand\cftsecfont{\LARGE}

\renewcommand\cftchappagefont{\LARGE\bfseries}
\renewcommand\cftsecpagefont{\LARGE}

\begin{document}

\tableofcontents

Some text in standard size just for comparison.