AP Style vs Chicago Style: A Complete Comparison
Two style guides dominate American English writing: the Associated Press Stylebook (AP Style) and the Chicago Manual of Style (Chicago Style). While both aim to ensure consistency and clarity, they evolved for different purposes and contain significant differences that writers need to understand.
This comprehensive guide breaks down the key differences between these two major style guides and helps you determine which one to use for your writing projects.
Origins and Primary Uses
AP Style
The Associated Press Stylebook originated in 1953 as a guide for journalists working at newspapers and wire services. It prioritizes brevity, clarity, and web readability. AP Style is the standard for:
- Newspapers and news websites
- Magazine journalism
- Press releases and public relations
- Blog posts and online content
- Marketing and advertising copy
Chicago Style
The Chicago Manual of Style first appeared in 1906 as a guide for book publishers at the University of Chicago Press. It’s comprehensive, covering virtually every aspect of writing and publishing. Chicago Style is the standard for:
- Book publishing (fiction and non-fiction)
- Academic writing in history and humanities
- Literary magazines and journals
- Long-form journalism and feature writing
- Business and technical documents
Key Differences at a Glance
| Element | AP Style | Chicago Style |
|---|---|---|
| Oxford comma | Not used (red, white and blue) | Used (red, white, and blue) |
| Em dash spacing | Spaces around (word — word) | No spaces (word—word) |
| Numbers | Spell out one through nine | Spell out one through one hundred |
| Percentages | Use % symbol (5%) | Spell out “percent” (5 percent) |
| State names | Traditional abbreviations (Calif.) | Spell out or use postal codes |
| Title capitalization | Capitalize words with 4+ letters | Capitalize major words |
| Time format | a.m., p.m. (lowercase) | AM, PM or a.m., p.m. |
The Oxford Comma Debate
Perhaps the most famous difference between AP and Chicago style is the treatment of the serial comma (also called the Oxford comma)—the comma before “and” or “or” in a list of three or more items.
AP Style: “We bought apples, oranges and bananas.”
Chicago Style: “We bought apples, oranges, and bananas.”
AP Style omits the serial comma to save space (a holdover from print journalism where every character counted). Chicago Style includes it for clarity, especially in complex sentences where the meaning could be ambiguous without it.
Consider: “I love my parents, Batman and Wonder Woman.” Without the Oxford comma, this could be read as saying your parents are Batman and Wonder Woman. With the comma: “I love my parents, Batman, and Wonder Woman” clarifies you’re listing three separate things.
Numbers and Numerals
The treatment of numbers is where these style guides diverge significantly.
AP Style Numbers
- Spell out numbers one through nine
- Use numerals for 10 and above
- Always use numerals for ages, percentages, dates, addresses, and monetary amounts
- Use the % symbol: “The vote passed with 67% approval”
Chicago Style Numbers
- Spell out numbers one through one hundred
- Spell out any number that begins a sentence
- Use numerals for technical or statistical content
- Spell out “percent”: “The vote passed with 67 percent approval”
Punctuation with Quotation Marks
Both styles agree that periods and commas go inside closing quotation marks in American English. However, they differ slightly in other punctuation scenarios.
Both styles: He said, “Hello.”
For colons and semicolons, both place them outside the quotation marks. The differences arise in more complex scenarios involving dialogue attribution and nested quotations.
Em Dashes and Spacing
The em dash—used for parenthetical statements and interruptions—is formatted differently:
AP Style: “The project — despite initial setbacks — was completed on time.”
Chicago Style: “The project—despite initial setbacks—was completed on time.”
AP Style includes spaces around em dashes for readability on screens and to prevent awkward line breaks in narrow columns. Chicago Style prefers no spaces, which is traditional in book typography.
Titles and Capitalization
Both styles use title case for headlines and book titles, but the rules differ slightly:
AP Style Title Case
- Capitalize words with four or more letters
- Capitalize verbs, even short ones (Is, Be, Are)
- Lowercase articles, conjunctions, and prepositions with three or fewer letters (a, an, the, and, but, or, for, of, to)
Chicago Style Title Case
- Capitalize all major words (nouns, verbs, adjectives, adverbs)
- Lowercase articles, prepositions, and coordinating conjunctions regardless of length
- Always capitalize the first and last word
Example title:
- AP: “A Journey Through the Mountains of the Pacific Northwest”
- Chicago: “A Journey through the Mountains of the Pacific Northwest”
Abbreviations and Acronyms
AP Style
- Uses traditional state abbreviations: Calif., N.Y., Fla.
- Spell out United States as a noun, abbreviate as U.S. as an adjective
- Generally spells out acronyms on first reference
Chicago Style
- Prefers spelled-out state names or postal codes: California, NY
- Either US or U.S. is acceptable if consistent
- More flexible with well-known acronyms
When to Use Each Style
Choose AP Style When:
- Writing news articles or journalism
- Creating press releases or media communications
- Writing blog posts or online content
- Developing marketing materials
- Writing for newspapers or magazines
- Working in public relations
Choose Chicago Style When:
- Writing books (fiction or non-fiction)
- Preparing academic papers in history or humanities
- Creating long-form content or features
- Working with book publishers
- Writing technical documentation
- When in doubt and no other style is specified
Consistency is Key
Regardless of which style you choose, consistency matters most. Mixing styles within a document creates confusion and appears unprofessional. Pick one style guide and follow it throughout your project.
Many organizations create their own style guides that borrow from both AP and Chicago, adapting rules to their specific needs. If you’re writing for a publication or organization, always ask for their house style guide first.
Tools for Style Compliance
Manually checking your writing against style guide rules is time-consuming. Our Typograph Tool and AP Style Title Case Converter can automatically apply typography and formatting conventions according to your chosen style guide, ensuring consistency throughout your document.
Conclusion
AP Style and Chicago Style serve different purposes, evolved from different traditions, and continue to be updated for modern writing needs. AP Style prioritizes brevity and digital readability, making it ideal for journalism and online content. Chicago Style emphasizes comprehensiveness and traditional book typography, making it the choice for publishing and academic writing.
Understanding both styles and knowing when to apply each one is a valuable skill for any professional writer. Whether you’re crafting a news article or preparing a manuscript, choosing the right style guide—and applying it consistently—elevates your writing to professional standards.