LaTeX Font Size - Complete Guide to Changing Font Sizes

\documentclass{article}
\begin{document}

{\tiny This is tiny text} \\
{\scriptsize This is scriptsize text} \\
{\footnotesize This is footnotesize text} \\
{\small This is small text} \\
{\normalsize This is normalsize text (default)} \\
{\large This is large text} \\
{\Large This is Large text} \\
{\LARGE This is LARGE text} \\
{\huge This is huge text} \\
{\Huge This is Huge text}

\end{document}

% 10pt base font (default)
\documentclass[10pt]{article}

% 11pt base font
\documentclass[11pt]{article}

% 12pt base font  
\documentclass[12pt]{article}

% With 10pt base
\documentclass[10pt]{article}
\begin{document}
\large % Produces 12pt text
\end{document}

% With 12pt base
\documentclass[12pt]{article}
\begin{document}
\large % Produces 14.4pt text (proportionally larger)
\end{document}

\documentclass{article}
\begin{document}

This is normal text. {\large This text is large.} Back to normal.

You can also use it for {\small smaller text} inline.

{\Large
This entire paragraph will be Large size
because the command is at the beginning
and the closing brace is after the paragraph.
}

\end{document}

\begin{center}
\large
This centered text is large.
Still large here.
\end{center}

This text is back to normal size.

\large
All text after this command is large.
This paragraph is large.
This one too.

\normalsize
% Return to normal size when done

% Custom section heading
\section{{\large Custom Size Section}}

% Or combine with other formatting
\section{{\Large\textbf{Large Bold Section}}}

% Title page with custom sizes
\begin{titlepage}
    {\Huge\bfseries Document Title}\\[1em]
    {\large Author Name}\\[0.5em]
    {\small\today}
\end{titlepage}

% Syntax: \fontsize{size}{baseline}\selectfont
\fontsize{14}{17}\selectfont

% Example: 14pt font with 17pt line spacing
{\fontsize{14}{17}\selectfont
This text is exactly 14 points with 17 points between baselines.
}

% Multiple custom sizes
{\fontsize{16}{20}\selectfont Large heading}\\[1em]
{\fontsize{11}{13}\selectfont Regular paragraph text}\\[0.5em]
{\fontsize{9}{11}\selectfont Small caption text}

% Resume header - large name
{\fontsize{24}{28}\selectfont\bfseries John Doe}\\[0.3em]

% Contact information - smaller
{\fontsize{10}{12}\selectfont
    john.doe@email.com | (555) 123-4567 | linkedin.com/in/johndoe
}

% Section headings - medium large
{\fontsize{14}{17}\selectfont\bfseries\scshape Experience}

% Job descriptions - standard
{\fontsize{11}{13}\selectfont
Regular body text for job descriptions and bullet points.
}

% Force display style in inline math
The sum $\displaystyle\sum_{i=1}^{n} i$ is large.

% Compare with normal inline (text style)
The sum $\sum_{i=1}^{n} i$ is compact.

% Large equation with custom text size
{\large
\begin{equation}
    E = mc^2
\end{equation}
}

% Changing base font affects math
{\footnotesize
The equation $a^2 + b^2 = c^2$ scales with text.
}

% anyfontsize package - allows any size
\usepackage{anyfontsize}
{\fontsize{23.5}{28}\selectfont Exact 23.5pt text}

% relsize package - relative sizing
\usepackage{relsize}
\larger\larger Text two sizes larger
\smaller Text one size smaller

% scalefnt package - scale current font
\usepackage{scalefnt}
\scalefont{1.5} % 150% of current size

% WRONG - affects all following text
This is normal. \large This is large and everything after!

% CORRECT - limited scope
This is normal. {\large This is large.} Back to normal.

% WRONG - \large doesn't affect internal math
$\large E = mc^2$ % Only "E" is affected

% CORRECT - wrap the entire environment
{\large $E = mc^2$} % Entire equation scales
% OR use displaystyle
$\displaystyle E = mc^2$

% WRONG - baseline too small causes overlap
{\fontsize{20}{18}\selectfont
This text will have overlapping lines
because baseline is smaller than font size.
}

% CORRECT - baseline should be 1.2× font size
{\fontsize{20}{24}\selectfont
Properly spaced text with adequate
line spacing for readability.
}

% WRONG - missing \selectfont
\fontsize{14}{17} This won't change size!

% CORRECT
\fontsize{14}{17}\selectfont Now it works!

\begin{titlepage}
    \centering
    \vspace*{2cm}
    
    {\Huge\bfseries The Impact of Quantum Computing}\\[0.5cm]
    {\huge on Modern Cryptography}\\[2cm]
    
    {\Large\itshape John Smith}\\[1cm]
    
    {\large Department of Computer Science\\
    University of Technology}\\[2cm]
    
    {\large\today}\\[3cm]
    
    \vfill
    {\small Submitted in partial fulfillment of requirements}
\end{titlepage}

\begin{center}
    {\fontsize{28}{34}\selectfont\bfseries JANE DOE}\\[0.2cm]
    {\fontsize{11}{13}\selectfont
        Senior Software Engineer | Full Stack Developer
    }\\[0.3cm]
    {\fontsize{10}{12}\selectfont
        jane.doe@email.com \textbullet\ +1 (555) 123-4567 \textbullet\ github.com/janedoe
    }
\end{center}

\documentclass[11pt,twocolumn]{article}
\begin{document}

{\LARGE\bfseries Article Title}\\[0.5em]
{\large Author Name}\\[1em]

\begin{abstract}
\small
This abstract uses a slightly smaller font to differentiate
from the body text while remaining readable.
\end{abstract}

\section{Introduction}
Body text at normalsize (11pt as specified in documentclass).

{\footnotesize
\begin{quote}
Block quotes can use footnotesize for subtle differentiation.
\end{quote}
}

\end{document}