Chicago author-date style cites sources in the text as (Author Year, page) and lists full details in a reference list at the end. It is the Chicago system used in the sciences and social sciences.
This guide follows the 18th edition of The Chicago Manual of Style, published in 2024, and flags where it differs from the 17th so you can match whichever edition your course requires.
Chicago Author-Date in Brief
In the text, write the author's surname and year with no comma between them: (Ramos 2021). Add a page number after a comma when you quote or refer to a specific passage: (Ramos 2021, 54).
At the end, list every source under the heading References, alphabetically by surname, with the year placed straight after the author's name.
Notes-Bibliography or Author-Date?
Chicago offers two systems. They contain the same information but present it differently, and a paper should use only one.
| Feature | Notes-bibliography | Author-date |
|---|---|---|
| Marker in text | Superscript note number | (Author Year, page) |
| Full details | Footnotes or endnotes, plus a bibliography | Reference list only |
| Year position in list | Near the end of the entry | Straight after the author |
| Usual fields | History, literature, arts | Sciences, social sciences, some business and education courses |
If your brief just says "Chicago", ask which system. History and literature tutors usually mean notes-bibliography.
In-Text Citation Format
Place the citation at the end of the clause or sentence it supports, before the full stop.
| Situation | Example |
|---|---|
| One author | (Ramos 2021) |
| With page number | (Ramos 2021, 54) |
| Two authors | (Ramos and Patel 2021) |
| Three or more authors (18th edition) | (Ramos et al. 2021) |
| Several sources | (Lee 2019; Ramos 2021) |
| Same author, same year | (Ramos 2021a, 2021b) |
| Organization as author | (World Bank 2023) |
| No date | (Ramos, n.d.) |
When you name the author in your sentence, put only the year, and any page, in brackets: Ramos (2021, 54) argues that housing policy lags behind migration.
The 17th edition used et al. only for four or more authors and listed all names for three. Check which edition your course follows.
Author-Date Citations in a Paragraph
Seeing citations inside real prose shows how placement and punctuation work together. The paragraph below uses three illustrative sources.
Mid-sized cities have grown faster than capitals in several regions over the past two decades (World Bank 2023). Ramos (2021, 54) links this growth to housing costs, arguing that "affordability now steers migration more than wages do." Others place more weight on transport links (Lee and Kim 2022; Patel 2020), although the evidence on commuting is mixed (Lee and Kim 2022, 210–12).
Notice three habits. The citation sits before the full stop. The narrative citation puts only the year and page in brackets. Multiple sources in one bracket are separated by semicolons, in an order you choose, often alphabetical or by date.
Locators Other than Pages
For sources without page numbers, such as e-books with reflowing text or web pages, cite a chapter, section or paragraph instead, for example (Nguyen 2023, under "Measuring rent"). Never invent page numbers from an e-reader's location count.
Citing the Same Work Repeatedly
Chicago author-date has no ibid. Repeat the citation each time, or give only the page number in brackets when it is obvious which source you mean and no other citation has intervened: (58).
The Reference List
Title the list References and start it on a new page. Arrange entries alphabetically by the first author's surname, invert only the first author's name, and use a hanging indent.
- Use headline-style capitalization for titles.
- Italicize titles of books, journals and websites; put article and chapter titles in quotation marks.
- List up to six authors. For seven or more, list the first three followed by et al. (18th edition).
- Repeat the author's name for every entry; do not replace it with a dash.
- Order several works by the same author by year, oldest first.
Under the 17th edition, entries listed up to ten authors, and more than ten became the first seven plus et al. The 18th also no longer requires the place of publication for books.
Books and Chapters
Book, one author
Ramos, Elena. 2021. Cities in Motion: Housing and Migration since 1990. Harbor University Press.
In text: (Ramos 2021, 112)
Book, two authors
Ramos, Elena, and Amit Patel. 2019. Planning the Shared City. Northfield Press.
Edited book
Okoye, Grace, ed. 2020. Urban Futures. Westbrook Books.
Chapter in an edited book
Patel, Amit. 2020. "Transit and Belonging." In Urban Futures, edited by Grace Okoye, 45–62. Westbrook Books.
These examples are illustrative. Under the 17th edition, add the city before the publisher, for example Boston: Harbor University Press.
Journal Articles
Give the journal title in italics, then the volume, the issue in brackets and the page range after a colon. Add a DOI as a full https://doi.org/ link where one exists.
Journal article with DOI
Lee, Daniel, and Sara Kim. 2022. "Commuting Time and Wellbeing in Mid-Sized Cities." Journal of Urban Studies 18 (3): 201–19. https://doi.org/10.0000/jus.2022.183
In text: (Lee and Kim 2022, 205)
Article from a database without a DOI
End the entry with the database name or a stable URL instead of a DOI.
Websites, Reports and Other Sources
Web page with an author
Nguyen, Thu. 2023. "How Cities Measure Affordability." Urban Data Notes. May 4, 2023. https://www.example.org/affordability.
Web page with no date
City Housing Trust. n.d. "Eligibility for Shared Ownership." Accessed March 2, 2025. https://www.example.org/eligibility.
Report by an organization
World Bank. 2023. Title of the Report. World Bank. https://www.worldbank.org/...
An access date is only needed when a source has no publication or revision date. For dated pages it is optional.
No Author
If there is no author, start the reference with the title and use a shortened title in the text, in italics or quotation marks as in the reference. For organizational content, the organization usually serves as author.
Chicago Author-Date vs APA 7
The two author-date styles look similar, which makes them easy to mix up. These are the differences that cost marks.
| Feature | Chicago author-date | APA 7 |
|---|---|---|
| In-text punctuation | (Lee 2022, 205) | (Lee, 2022, p. 205) |
| Author names in list | Full first names | Initials |
| Article titles | Headline case, in quotation marks | Sentence case, no quotation marks |
| Book titles | Headline case, italics | Sentence case, italics |
| Year in list | 2022. | (2022). |
| Three authors in text | et al. (18th edition) | et al. |
If you are switching a paper from APA to Chicago, change one feature at a time across the whole list: names first, then titles, then punctuation. The free Bibloq citation generator can produce Chicago entries to compare against.
Common Chicago Author-Date Mistakes
- Adding a comma between author and year: write (Ramos 2021), not (Ramos, 2021).
- Writing "p." before page numbers, which Chicago does not use in author-date citations.
- Mixing footnote citations with author-date citations in one paper.
- Placing the year at the end of the reference entry instead of after the author.
- Using the 17th edition's et al. rules when your course has moved to the 18th, or the reverse.
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Frequently Asked Questions
Turabian is the student version of Chicago and offers the same two systems. Its author-date format follows the matching Chicago edition closely, with extra guidance for student papers.
Not for citations. Footnotes may still be used for comments or explanations, but sources are cited in the text.
References. Notes-bibliography uses Bibliography instead.
Only when you quote or refer to a specific passage. A citation for a whole work needs just the author and year.
Only when the page has no publication or revision date, or if your instructor asks for them.
Under the 18th edition, use the first author plus et al. in the text. Under the 17th, name all three. The reference list names all of them in both editions.
The 18th edition no longer requires it. The 17th edition includes the city before the publisher.
Chicago itself allows single spacing within entries with a blank line between them, but many instructors ask for double spacing throughout. Follow your course guidance.
Chicago prefers that you consult the original. If you cannot, cite both in the text, for example (Morris 1998, 22, quoted in Ramos 2021, 60), and list the source you actually read.
Chicago's own system shortens some ranges, such as 201–19, but full ranges are always clear. Follow your instructor if they specify one form, and stay consistent.