Chicago Style Title Case Rules Explained | TitleCasePro

Chicago style title case is defined by the Chicago Manual of Style (CMOS), 17th edition. It is the standard for book publishing, history, and humanities. Chicago uses a preposition-length rule: short prepositions (four letters or fewer) stay lowercase, but longer prepositions (five letters or more) are capitalized.

The defining rule: Prepositions of ≤ 4 letters are lowercase. Prepositions of 5+ letters are capitalized. This length-based approach is what most distinguishes Chicago from APA and MLA, which lowercase all prepositions regardless of length.

Chicago Title Case Rules

According to CMOS 17:

1. Capitalize the first and last word of the title and subtitle, always.
2. Capitalize all major words: nouns, verbs, adjectives, adverbs, and pronouns.
3. Lowercase articles: a, an, the (unless first or last word).
4. Lowercase coordinating conjunctions: and, but, or, nor, for, so, yet.
5. Lowercase prepositions of four letters or fewer: at, by, for, in, of, on, to, up, as, off, out, per, via, into (4), from (4), over (4), like (4), onto (4), down (4), with (4), upon (4).
6. Capitalize prepositions of five or more letters: About (5), Above (5), After (5), Along (5), Among (5), Below (5), Since (5), Under (5), Until (5), While (5), Against (7), Around (6), Before (6), Behind (6), Beside (6), Between (7), Beyond (6), During (6), Except (6), Inside (6), Toward (6), Through (7), Within (6), Without (7).
7. The infinitive “to” is a preposition in CMOS and stays lowercase.
8. Hyphenated compounds: capitalize both elements, unless the second element is an article, preposition, or coordinating conjunction.

Chicago Title Case Examples

The preposition length rule in action

Title	Note
A Guide to Writing About the Environment	to (2 letters) → lowercase; About (5 letters) → Capitalize
The Conflict Between Science and Religion	Between (7 letters) → Capitalize
Living Without Fear: A Practical Approach	Without (7 letters) → Capitalize
The Art of Writing in the Modern World	of (2), in (2), the → all lowercase

⚠️ Common confusion: with has exactly 4 letters. Chicago’s rule is “4 letters or fewer” — so with is lowercase in Chicago. Don’t capitalize it.

Subtitle rule

The Art of Writing: A Complete Guide for Beginners — “A” after the colon is capitalized because it begins the subtitle.

Verb rule

Why Mindfulness Is Good for Students — Is → capitalize (verb). for → lowercase (preposition, 3 letters). Good → capitalize (adjective).

The 4-Letter Boundary: Quick Reference

Letters	Treatment	Examples
1–4	Lowercase	at, by, for, in, of, on, to, up, via, off, into, from, over, like, with, upon, down, onto
5+	Capitalize	About, Above, After, Along, Among, Below, Since, Under, Until, Against, Around, Before, Between, Beyond, During, Through, Without

Memory tip: Count the letters. With = 4 → lowercase. About = 5 → Capitalize. When in doubt, count.

Chicago vs. APA: The Key Difference

The most visible difference between Chicago and APA is how they handle medium and long prepositions.

Preposition	APA	Chicago
about (5)	lowercase	Capitalize
between (7)	lowercase	Capitalize
through (7)	lowercase	Capitalize
without (7)	lowercase	Capitalize
with (4)	lowercase	lowercase
from (4)	lowercase	lowercase

Same title, two styles:

• APA: A Comprehensive Study of the Conflict between Science and Religion
• Chicago: A Comprehensive Study of the Conflict Between Science and Religion

Only the capitalization of “Between” changes — everything else is identical. But this one word is the difference between correct and incorrect formatting in each style.

For a direct side-by-side comparison, use the APA vs Chicago comparison guide or the compare all styles tool.

Where Chicago Title Case Is Used

Chicago style is expected in:

• Book publishing across most genres (fiction, non-fiction, academic monographs)
• History and humanities journals
• Art, music, and film criticism
• General-audience magazines and essays
• US university presses (Chicago, Harvard, Oxford)
• Chicago-formatted theses and dissertations

Tip: Use the Chicago title capitalizer to apply CMOS 17 rules accurately, with a word-by-word breakdown explaining why each preposition was capitalized or lowercased.