# Make font-size smaller

I've this heading in the first tex file - for a computer science thesis:

\documentclass[10pt,a4paper,twoside,openright]{book}
\usepackage[italian,english]{babel}
\usepackage[utf8x]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{listings}
\usepackage[top=1in, bottom=1.5in, left=1.2in, right=1in]{geometry}
\usepackage{graphicx}
\usepackage{fancyhdr}
\usepackage{float}
\usepackage[hyperindex]{hyperref} %per l'indice interattivo
\usepackage[all]{hypcap}    % utilizzato per far riferimento ad un'immagine, e non al suo caption
\usepackage{lipsum}
\usepackage{esvect}
\usepackage{minted}
\usepackage{caption}
\usepackage{pgfplots}
\usepackage{emptypage}
\pgfplotsset{compat=1.14}

\def\changemargin#1#2{\list{}{\rightmargin#2\leftmargin#1}\item[]}
\let\endchangemargin=\endlist

\graphicspath{ {img/} }

\setcounter{secnumdepth}{2}
\setcounter{tocdepth}{1}

\newcommand{\HRule}{\rule{\linewidth}{0.5mm}}

\newcommand{\fncyblank }{\fancyhf{}}
\newenvironment{abstract}%
{\cleardoublepage\fncyblank\null \vfill\begin{center}%
\bfseries \abstractname \end{center}}%
{\vfill\null}


and I would make the font-size smaller (10pt to 9pt). Due to the 9pt size, I've to use extbook document class. The problem is that the difference between 10pt and 9pt is too big. How could I make the font-size a bit smaller?

Thanks!

• If you use a font that also has intermediate font sizes (e.g. \usepackage{lmodern}), you could do something like \fontsize{9.5pt}{11pt}\selectfont text – user36296 Apr 10 '18 at 14:24
• Normal LaTeX font sizes (\normalsize, \small, \footnotesize...) have a roughtly 1.2 (or .8333 decreasing) scale factor between successive sizes. – John Kormylo Apr 10 '18 at 14:42
• The solution has generated the same result as the extbook with 9pt solution. – Federico Cuozzo Apr 10 '18 at 18:21