Title case in APA, Chicago and AP style: which small words stay lowercase

Title case looks like one rule and is three. The house style you write for decides whether “with”, “from” or a final “of” keeps its capital, and the most widely copied description of Chicago’s rule stopped being true in September 2024.

What the three guides say

Title case capitalises the major words of a title and lowercases a defined set of minor ones. Sentence case, by contrast, capitalises only the first word and proper nouns. The guides agree on the outline: articles are minor, nouns, verbs, adjectives, adverbs and pronouns are major, and the first word is always capitalised. They part company on prepositions, conjunctions and the last word.

	APA (7th edition, §6.17)	Chicago (18th edition, 8.160)	AP Stylebook
Articles	Lowercase	Lowercase	Lowercase
Conjunctions	Lowercase if three letters or fewer	Lowercase and, but, for, or, nor only	Lowercase if three letters or fewer
Prepositions	Lowercase if three letters or fewer	Lowercase if four letters or fewer	Lowercase if three letters or fewer
“to” and “as”	Lowercase	Lowercase in every use	Lowercase
Last word	No special rule	Always capitalised	Always capitalised
After a colon	Capitalised, also after an em dash	Capitalised	Capitalised
Words of four letters or more	Always capitalised	Capitalised unless a short preposition	Always capitalised

APA’s own wording is that minor words are “short (i.e., three letters or fewer) conjunctions, short prepositions, and all articles”. AP’s is to capitalise “the principal words, including prepositions and conjunctions of four or more letters”.

The Chicago change most converters missed

From its 12th edition to its 17th, Chicago lowercased prepositions “regardless of length”. The 18th edition, published in 2024, capitalises prepositions of five letters or more. Chicago’s own Q&A gives the effect on a real title: “Health Disparities among Communities throughout the Nation” under the 17th edition becomes “Health Disparities Among Communities Throughout the Nation” under the 18th.

Four-letter prepositions such as “with”, “from”, “into” and “over” are still lowercase in Chicago, which is now the clearest line between it and the other two. The 18th edition also stopped lowercasing the second part of a compound after a prefix, so “Non-Traditional” and “T-Shirt” keep both capitals.

The same headlines in each style

Input	APA	Chicago	AP
working with the people behind a brand	Working With the People Behind a Brand	Working with the People Behind a Brand	Working With the People Behind a Brand
notes from a self-taught designer: what PDF files are made of	Notes From a Self-Taught Designer: What PDF Files Are Made of	Notes from a Self-Taught Designer: What PDF Files Are Made Of	Notes From a Self-Taught Designer: What PDF Files Are Made Of
colour: a primer for print	Colour: A Primer for Print	Colour: A Primer for Print	Colour: A Primer for Print

Two details carry most of the difference. “From” has four letters, so APA and AP capitalise it and Chicago does not. The final “of” is a short preposition, so APA lowercases it while Chicago and AP capitalise any last word.

Hyphens, acronyms and the limits of a word list

In a hyphenated compound the first part is always capitalised and the later parts follow the minor-word rule: “Self-Report”, “Up-to-Date”, “Long-Term”. Acronyms and names with an internal capital, such as PDF, NASA or McLaren, keep their own capitals.

No style guide can be applied perfectly by a list. “Up” is a preposition in “Up the Hill” and an adverb in “Give Up”, and all three guides capitalise the adverb because it is a major word. A converter working from word lists lowercases “up” wherever it falls mid-title, so phrasal verbs (log in, set up, sign out) are worth a second look.

Convert a title with the tool

1. Open the case converter and paste into Your text. Each line is treated as its own title, so a list of headings converts in one go.
2. Leave Keep acronyms like PDF and NASA ticked unless the text is in capitals throughout, in which case the tool cannot tell an acronym from a shouted word and lowercases everything first.
3. Read the three results, Title Case · APA, Title Case · Chicago and Title Case · AP, side by side, and press the copy button on the one your publication uses.
4. For text in Turkish, Azerbaijani, German or Dutch, choose it under Language rules first; see the next section.

The same page also gives sentence case, UPPERCASE, lowercase, camelCase, PascalCase, snake_case, kebab-case and CONSTANT_CASE, all at once.

Two languages that break naive converters

JavaScript’s toUpperCase() follows rules with no language, and toLocaleUpperCase() with no argument follows the visitor’s browser. Turkish has a dotted and a dotless i: “istanbul” must become “İSTANBUL”, and “IŞIK” must lowercase to “ışık”, not “işik”. The tool passes the language you pick, so the result does not depend on how the computer is set up.

German ß uppercases to “SS” under the default rules, which cannot be reversed, because “ss” is also correct German. Since 2017 the Council for German Orthography allows a capital ẞ, and Uppercase ß as ẞ, not SS uses it, so “straße” becomes “STRAẞE” and lowercases back to “straße”. The title-case styles themselves are English: German titles capitalise nouns, so use sentence case for German text.

Other ways to change case

Google Docs has Format → Text → Capitalisation, with a title-case option that capitalises every word. Microsoft Word’s Change Case button (Aa on the Home tab) has “Capitalise Each Word”, which also ignores minor words. On a command line, tr '[:lower:]' '[:upper:]' uppercases a file but, in many setups, only the letters A to Z. None of them applies APA, Chicago or AP.

Checking that nothing is uploaded

Open developer tools on the Network tab and type: no request goes out. The text is kept in this browser’s storage between visits and nowhere else.

For checking the length of the finished headline against an ad or a post limit, the word counter counts it the way each platform does; its guide covers why word and character counts differ.