Chicago Title Capitalization Rules
CMOS 17 capitalises all major words. Short prepositions (≤4 chars) are lowercase, but longer ones like "About" and "Between" are capitalised.
Word-by-word explanation
Chicago Capitalization Rules
- Capitalise all major words
- Lowercase: articles (a, an, the)
- Lowercase: coordinating conjunctions (FANBOYS)
- Lowercase: prepositions ≤4 letters (at, by, for, in, of, on, to)
- Capitalise: prepositions ≥5 letters (About, Above, Between…)
- Always capitalise first and last word
- Capitalise both parts of a hyphenated compound
Source for These Chicago Rules
Primary source
The Chicago Manual of Style
- Edition
- 17th edition
- Year
- 2017
- Published by
- University of Chicago Press
Headline-style capitalization is set out in CMOS §8.157. The engine implements its preposition-length rule: prepositions of four letters or fewer stay lowercase, longer prepositions are capitalized, and “to” as an infinitive marker stays lowercase.
TitleCasePro is not affiliated with, endorsed by, or a substitute for the publisher above. For how these rules were turned into code, which edge cases the engine decides for you, and how the results are tested, read the methodology. If you believe a rule here is wrong, tell us and cite the section you are reading.
Where Chicago Title Case Is Used
Chicago title capitalization is the standard for Books, Publishing, History, Arts & Humanities writing. When your work will be reviewed, published, or cited within these fields, using the correct capitalization shows attention to detail and compliance with professional standards. If your publication specifies a house style, follow that preference over the base standard.
How Chicago Style Works in Practice
Chicago title case is defined by the Chicago Manual of Style, 17th edition (2017), and is the standard for book publishing, academic monographs, history writing, and general non-fiction. Chicago uses a preposition-length rule: prepositions of four letters or fewer (at, by, for, in, of, on, to, up, with, from, into, over) stay lowercase, while prepositions of five or more letters (About, Above, Across, After, Among, Between, Beyond, During, Through, Without) are capitalized. This puts Chicago between the other styles rather than beside any one of them. MLA lowercases prepositions of every length, so "A Study About the World" capitalizes "About" in Chicago but not in MLA. APA and AP go the other way and capitalize every word of four letters or more, so "Living With Uncertainty" and "Letters From Home" take capitals in APA and AP while Chicago keeps "with" and "from" down. The practical way to apply this is to count letters rather than argue about grammar. Four letters or fewer, and the preposition stays lowercase: at, by, for, in, of, on, to, up, from, into, like, near, next, onto, over, past, plus, with. Five letters or more, and it is capitalized: About, Above, Across, After, Among, Before, Behind, Beyond, During, Inside, Since, Through, Toward, Under, Until, Without. Articles and coordinating conjunctions are lowercase mid-title whatever their length, and the first and last words are always capitalized.
How the Chicago Capitalizer Works
Paste your title into the tool above. Chicago is already selected, so the result appears immediately. Click "Explain" to see the rule applied to each word. Use the copy button or press ⌘↵ to copy the output. Everything runs in the browser — no account, no signup, no data sent to a server.
To convert a list of titles at once, the batch capitalizer imports CSV and TXT files. To see one title in all nine styles simultaneously, use the style comparison tool.
Chicago Title Case Examples
These examples are generated in real time by the same engine that powers the tool above — every result is guaranteed to match the tool's output.
| Original (lowercase) | Chicago Style |
|---|---|
| the quick brown fox jumps over the lazy dog | The Quick Brown Fox Jumps over the Lazy Dog |
| a guide to writing about the world | A Guide to Writing About the World |
| why sleep is important for students | Why Sleep Is Important for Students |
| learning through failure and success | Learning Through Failure and Success |
| notes on the art of writing without fear | Notes on the Art of Writing Without Fear |
| how to capitalize titles in academic writing | How to Capitalize Titles in Academic Writing |
| the effects of social media on mental health | The Effects of Social Media on Mental Health |
| introduction to machine learning with python | Introduction to Machine Learning with Python |
Common Edge Cases in Chicago Style
- "With" has exactly 4 letters — it stays lowercase in Chicago even though it looks substantial.
- "Into" (4 letters) stays lowercase. "Until" (5 letters) gets capitalized.
- Coordinating conjunctions "so" and "yet" are lowercased here in every position except first and last. CMOS notes that they are capitalized when they act as adverbs rather than conjunctions, but part of speech cannot be detected from the word alone, so this is a manual fix after converting — the engine always lowercases them.
- First and last word are always capitalized, even if they are short prepositions like "of" or "in."
- The first word after a colon is always capitalized. The second part of a subtitle starts with a capital.
- Hyphenated compounds follow CMOS §8.157: capitalize both elements, unless the second element is an article, a preposition, or a coordinating conjunction. That is why Chicago gives "Well-Known" and "Self-Report" but "State-of-the-Art" and "Up-to-Date" — the inner "of," "the," and "to" are lowercase words carried inside the compound.
- The first element of a hyphenated compound is always capitalized, even when it is a short word that would be lowercase on its own.
How Chicago Differs From Bluebook
Chicago and Bluebook produce nearly identical title case because Bluebook's rules closely follow Chicago's preposition-length threshold. Both capitalize prepositions of five or more letters and lowercase shorter ones. The main practical differences appear in citation formatting rather than in title case itself. Bluebook adds legal-specific rules for case names, statutes, and abbreviations, while Chicago is the broader publishing standard. For general title capitalization of headings and article titles, the two styles are interchangeable.
Chicago Title Capitalization FAQ
Common questions about Chicago title case rules and the Chicago capitalizer.
Chicago title capitalization follows the Chicago Manual of Style, 17th Edition (CMOS 17). It capitalizes all principal words and lowercases articles, coordinating conjunctions, and prepositions of four or fewer letters. Prepositions of five or more letters — "About," "Above," "Between," "Through," "Without" — are capitalized.
Use Chicago title case for books, book chapters, journals, magazines, and academic work in history and humanities. Most US publishers, including university presses, follow the Chicago Manual of Style.
Principal words — nouns, pronouns, verbs, adjectives, adverbs, subordinating conjunctions — are capitalized. Longer prepositions (five or more letters) like "About," "Above," "Across," "Against," "Between," "Through," and "Without" are also capitalized.
Articles (a, an, the), coordinating conjunctions (and, but, or, nor, for, so, yet), and prepositions of four or fewer letters (at, by, for, in, of, on, to, up, via, with, from, into, onto, over, down, like, than) are lowercase in the middle of a Chicago title.
No. Articles (a, an, the) are lowercase in the middle of a Chicago title. The exception: the first and last words of a title are always capitalized, so "A," "An," or "The" is capitalized when it opens or closes the title.
Coordinating conjunctions (and, but, or, nor, for, so, yet) are lowercase. Subordinating conjunctions (because, although, when, since, while, unless) are principal words and are capitalized in Chicago style.
Short prepositions (four or fewer letters) are lowercase: at, by, for, in, of, on, to, up, via, from, into, like, onto, over, down, than, with. Longer prepositions (five or more letters) are capitalized: About, Above, Across, After, Against, Among, Between, Beyond, During, Except, Through, Under, Until, Without.
Yes. The first word of a Chicago title is always capitalized, regardless of part of speech.
Yes. The last word of a Chicago title is always capitalized, regardless of part of speech.
Chicago's key distinction is its 4-letter cutoff: prepositions of four or fewer letters go down, longer ones like "About" and "Between" are capitalized. APA and AP both capitalize all 4+ letter words — so they capitalize "from" and "with," which Chicago lowercases. MLA goes the other way and lowercases all prepositions regardless of length.
Yes. Use the Chicago title capitalizer to convert any title and see a word-by-word explanation.
Yes. The Compare Styles tool shows all 9 styles side by side for any title you enter.
Yes. TitleCasePro follows CMOS 17 rules. Use the Title Capitalizer for single titles or the Batch Capitalizer for lists.
The Chicago title capitalizer converts any title into correct Chicago Manual of Style (CMOS 17) capitalization instantly. Select Chicago, paste your title, and see the result with an optional word-by-word explanation.
Chicago capitalizes the first and last word plus all major words — nouns, verbs, adjectives, adverbs, pronouns. Articles (a, an, the), coordinating conjunctions, and prepositions of four or fewer letters are lowercase. Longer prepositions like "About," "Between," and "Through" are capitalized.
Yes. TitleCasePro follows the Chicago Manual of Style, 17th Edition. Short prepositions (≤4 letters) like "at," "by," "for," "in," "of," "on," "to," "up" are lowercase. Prepositions of five or more letters are capitalized.
It capitalizes principal words — nouns, pronouns, verbs, adjectives, adverbs — and lowercases articles, coordinating conjunctions, and prepositions of four or fewer letters. The first and last words are always capitalized regardless of type.
Yes. Click "Explain" to see each word labeled with its rule — for example, "from — preposition ≤4 letters, lowercase per Chicago CMOS §8.157."
Yes. Click the Copy button or press ⌘↵ to copy the result to your clipboard.
Yes. The Compare Styles tool shows Chicago alongside APA, AP, MLA, and 5 other styles in one table.
Yes. Chicago is the standard for book chapters, journal articles, and headings in general publishing. Paste your title and copy the correctly formatted result.
Yes. History and humanities essays commonly follow Chicago. The capitalizer applies the correct CMOS rules to your essay title automatically.
Yes. Chicago is the standard for most book publishing. Paste your book or chapter title and the tool formats it to CMOS 17 rules.
Yes. Chicago title case applies to headings, chapter titles, and section titles in books and long-form documents. The tool handles all of these correctly.
Yes. Completely free with no account or usage limit required.
Yes. Runs entirely in your browser — no server, no storage, works on desktop and mobile.