Chicago Style Format Guide: Notes-Bibliography vs Author-Date

Short answer: Chicago offers two systems: notes-bibliography (footnotes plus a bibliography, used in history and the humanities) and author-date (parenthetical citations plus a reference list, used in the sciences).

Choosing the wrong Chicago system is the most common formatting error students make. Check your discipline first, then follow the patterns below.

Notes-Bibliography Footnote Formats

1. First note: 1. Sarah Mitchell, Writing Under Pressure (Chicago: Ridgeline Press, 2023), 41.
2. Shortened note: 2. Mitchell, Writing Under Pressure, 55.
3. Journal note: 3. Alan Nguyen, "Revision Habits," College Composition 71, no. 2 (2024): 90.
4. Website note: 4. Maya Ortiz, "Study Skills That Stick," LearnWell, March 12, 2024, https://learnwell.org.

Author-Date Patterns

1. In-text: (Mitchell 2023, 41)
2. Reference: Mitchell, Sarah. 2023. Writing Under Pressure. Chicago: Ridgeline Press.
3. Two authors in text: (Mitchell and Nguyen 2024, 12)

Manuscript Formatting

1. Double-space body text; single-space footnotes with a blank line between them
2. 1-inch margins and a 12pt serif font
3. Page numbers in the header, starting on the first page of text
4. Bibliography entries alphabetized with hanging indents

How to Choose the Right Topic

Step 1. Ask your instructor which Chicago system the assignment requires.

Step 2. Insert footnotes with your word processor so numbering updates automatically.

Step 3. Use the full note the first time a source appears, then shortened notes after.

Step 4. Build the bibliography as you write rather than at the end.

Step 5. Check that every footnote source also appears in the bibliography.

Common Mistakes to Avoid

• Picking a topic so broad you cannot cover it in the assigned page count


• Choosing a subject with no credible, peer-reviewed sources available


• Restating an argument without adding your own analysis or evidence


• Ignoring your instructor's rubric, required citation style, or page limits


• Leaving topic selection until the night before the deadline

Frequently Asked Questions

Is Turabian the same as Chicago?

Turabian is a student-focused adaptation of Chicago. The citation formats are essentially identical with minor differences in paper formatting.

Do I need both footnotes and a bibliography?

In notes-bibliography style, yes — unless your instructor waives the bibliography for short papers with complete first notes.

Should I use ibid.?

Chicago 17 discourages ibid. in favor of shortened notes, which are clearer for readers scanning citations.

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