How to set LaTeX font size and title font size

Key points of this article

The entire text size is written in the square brackets of \documentclass, such as 11pt; when only changing part of the text, use the font size command plus curly brackets to group it.
It is recommended to use the titlesec macro package to set the chapter title font size and numbering symbols in a unified manner, which is more stable than manually changing them one by one, and the table of contents is also less prone to errors.
The table font size can be grouped to wrap the tabular, which will not affect the table notes and text; if it cannot fit, consider column width wrapping or scaling according to the width.
Inline formulas follow the font size of the text where they are located. To enlarge a formula individually, you can use the zoom command to avoid changing global settings.
Compile once after making the changes, and check one by one whether the paging, the table exceeds the center of gravity, and whether the warnings and formulas in the compilation log are still correct.

When writing a LaTeX paper or report, the first trouble many people encounter is not the formatting command itself, but the font size: the text wants to be smaller, the chapter titles need to stand out, the table is too wide to fit, and the inline formulas appear too small. These requirements look similar, but the actual corresponding settings are different. If you make the wrong changes, it will either not take effect or the layout of the entire document will be distorted.

This article is written for people who are writing documents in LaTeX and need to adjust the font size. It will be explained clearly in four categories: text size, title font size and numbering symbols, table fonts, and formula sizes. Font styles (font families, Chinese font selection, etc.) are outside the scope of this article. After reading, you will be able to determine whether to change document class options, local commands, or a certain macro package, and know how to check the results.

If you have a LaTeX source code package and want to translate it into another language first, OmniDoc's document translation supports LaTeX source code packages and will retain formulas and tables. The translation also needs to be recompiled in LaTeX to check the font size, and the machine-translated content also needs to be manually checked.

How to set font size in LaTeX? One sentence conclusion

Change the text size to the document class option, use the font size command plus curly brackets for local text, use the titlesec macro package for titles, and use the grouping or scaling commands for tables and formulas. The four types of changes have different scopes. Choosing the right location is more important than remembering the command.

your situation	Recommended practices	reason
I want to change the font size of the entire text	In the square brackets of \documentclass write 11pt or 12pt	Unify the entire text, affecting the base font size of paragraphs and default titles.
I just want to make certain paragraphs or words smaller	Use font size commands such as {\small text} and group them with curly braces	The scope is limited to curly braces and does not affect other paragraphs.
I want to uniformly change the font size and numbering format of chapter titles.	Use the \titleformat setting of the titlesec package	One setting takes effect on all titles of the same level, making subsequent modifications easier.
The table or formula is too large or too small	The table is wrapped in tabular with grouping; the formula is scaled with grouping or \scalebox	The font size only affects the table or formula itself and does not affect the layout of the text.

Before you start: Confirm these points first

Knowing the templates, macro packages and modification objects before you start can avoid most "modified but no change" situations.

Confirm the font size options supported by the document class. Standard article, report, and book support three writing methods: 10pt, 11pt, and 12pt. Templates provided by schools or journals often have their own font size regulations. You should read the template description first before deciding whether to change it, otherwise the format may not meet the requirements when submitting.
Confirm which layer is changed. Text, titles, tables, formulas, and table notes have different setting positions. First find out which category the text you want to change belongs to in the source code, and then start. It is much faster than repeated trial and error.
Check whether the title macro package has been loaded. titlesec needs to be written in the introductory area and earlier than \begin{document}. If the template has already defined the title format, adding a set of settings may overwrite each other, and the results will not meet expectations.
Keep compilable backups. Before changing the font size, make a copy of the source file that can be compiled normally. Changes in font size often lead to changes in paging and chart positions, so you can quickly roll back with a backup.
Confirm the compilation environment. The layout details of the same source code may be slightly different under different distributions or compilation engines. It is recommended to use the same environment to complete modification and checking.

Steps to adjust title font size in LaTeX

The following takes chapter titles (\section and \subsection) as an example, and uses the titlesec macro package to uniformly set the font size and numbering format.

Open the main .tex file and find the introductory area, which is the part before \begin{document}.
Add \usepackage{titlesec} in the introductory area. If the template has already loaded the macro package, skip this step and go directly to the next step.
Write \titleformat{\section}{\Large}{\thesection}{1em}{} and replace \Large with the required font size command, such as \large, \LARGE. This line controls the distance between the font size and the number.
If the section title also needs to be adjusted, write another \titleformat{\subsection}{\large}{\thesubsection}{1em}{}, and choose a font size one step smaller than the chapter title.
Use \titlespacing to adjust the spacing before and after the title, for example \titlespacing*{\section}{0pt}{12pt}{6pt}. When the font size is increased, the title and body text are likely to be squeezed together. This step can make the layout more even.
Compile twice. The table of contents and cross-references usually require a second compilation before they are updated. Check the title effect and table of contents page numbers after two compilations.

Check each item after completion

Compiling successfully does not mean the effect is correct. A step-by-step inspection can reveal hidden problems caused by font size changes.

Check items	How to see	What to do if there is a problem
Are the text sizes consistent?	Flip through a few pages at random and compare the baseline font sizes of paragraphs.	Check whether the curly braces are missing in commands such as \small, or whether the document class option is written in the correct position
Title font size and number	Compare the display effects of titles at all levels with those in the table of contents	Verify that the titlesec setting is before \begin{document} and does not conflict with the title definition in the template
Does the table exceed the bounds of publication?	Check whether the right edge of the table exceeds the text width	Reduce font size, or use p{} column width to wrap cells; use \resizebox if necessary, graphicx package is required
Are the formula sizes coordinated?	Compare the visual height of inline formulas and body text	Inline formulas follow the text number. Single formulas are scaled with \scalebox. Do not modify global math settings.
Compilation log	See warnings for Overfull \hbox and undefined commands	Modify one by one according to the line number in the log. The warning usually points directly to the problem location.

If the document contains translations obtained through OmniDoc translation, it should also be recompiled and checked according to the table above. The professional terminology, formula descriptions and table notes in the translation need to be manually checked against the original text, not just whether the typesetting is normal.

📊 Core comparison

Setting method	Scope	Suitable situation
Document class options (e.g. 11pt)	Baseline font size for full-text text and default titles	Need to uniformly adjust the text size of the entire article
Font size command is grouped by curly braces	Text, tables or partial paragraphs within curly braces	Only change one part of the content without affecting other parts
titlesec package	All headings at the same level	Title font size, numbering and spacing need to be set uniformly
\scalebox or \resizebox scaling	Specified table, picture or formula	The content has been formatted, you just need to scale the entire content to fit the format.

❓ Frequently Asked Questions (FAQ)

1. I wrote \large in the introduction area, why is there no change in the main text?

Writing the font size command directly in the introduction area will not change the base font size of the main text. The main text size is determined by the document class option. To change the entire text, the font size should be written in square brackets within \documentclass.

2. When the font size of the table becomes smaller, will the font size of the table notes also change?

When only wrapping the grouping in tabular, table captions will not be affected, because table captions are usually controlled by caption alone. If the grouping is placed outside the entire table environment, the table annotations will also change together. You need to select the position according to the desired effect.

3. The size of the formula and text are inconsistent. Where should I change it?

Inline formulas follow the text size. After correcting the text size, the formulas will change together. When you only need to enlarge or reduce a certain formula, use \scalebox or group processing to avoid changing the global mathematical settings.

4. After adding titlesec, a compilation error is reported. How to troubleshoot?

First check the error line number to confirm whether it conflicts with the existing title definition in the template, or whether \titleformat is written after \begin{document}. By checking each item before compiling, the problem can usually be quickly located.

📝 Summary

The key to how to set the font size in LaTeX is to first determine the scope of the change: use the document class option for the full text, group using the font size command for parts, use titlesec for the title, and use grouping or scaling for tables and formulas. After completing the modification, compile twice and check the paging, table width and compilation log one by one to confirm that the effect meets the requirements.

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