Chicago style is one of the most widely used citation systems in academic writing, and it is unusual because it offers two complete ways to cite sources. This guide explains how chicago style works, when to use each of its two systems, and how to format footnotes, in-text citations, and bibliography entries correctly, with clear examples you can follow.
What is Chicago style?
Chicago style comes from The Chicago Manual of Style, currently in its 18th edition (published 2024), with the 17th edition (2017) still in common use. It is published by the University of Chicago Press and is favored in history, the humanities, and many social sciences.
The defining feature of chicago style is that it supports two distinct documentation systems. You choose one and use it consistently throughout a paper. Your instructor, journal, or publisher usually tells you which one to use.
- Notes and Bibliography (NB): uses numbered footnotes or endnotes plus a bibliography. Common in history, literature, and the arts.
- Author-Date: uses brief parenthetical citations in the text plus a reference list. Common in the sciences and social sciences.
If you have been asked to use the student-focused version of Chicago, that is usually Turabian style, which follows the same two systems with small adjustments for coursework.
The Notes and Bibliography system
In the NB system you place a superscript number in the text at the end of the sentence or clause you are citing. That number points to a footnote at the bottom of the page (or an endnote at the end of the document). You then list every source again in an alphabetized bibliography.
First footnote and the bibliography entry
The first time you cite a source, the footnote gives the full details. The bibliography entry contains the same information but is formatted differently: the author’s name is inverted, periods replace some commas, and publication facts are not placed in parentheses.
Bibliography: Smith, John. The History of Citation. Chicago: University of Chicago Press, 2020.
First footnote: 1. John Smith, The History of Citation (Chicago: University of Chicago Press, 2020), 45.
Notice the differences. In the footnote the author appears in normal order (John Smith), the publication facts sit in parentheses, and a specific page number (45) shows exactly where the information came from. In the bibliography the name is inverted (Smith, John), elements are separated by periods, and no page number appears because the entry refers to the whole work.
Shortened footnotes
After the first full footnote, every later citation of the same source uses a shortened form: the author’s last name, a short version of the title, and the page number. This keeps notes readable.
Bibliography: Smith, John. The History of Citation. Chicago: University of Chicago Press, 2020.
Shortened footnote: 2. Smith, History of Citation, 78.
Older editions allowed the Latin abbreviation “Ibid.” for a source cited immediately before. The 17th and 18th editions discourage it and recommend the shortened form instead, so use the short note shown above.
A journal article in Notes and Bibliography
Journal articles add the article title in quotation marks, the journal name in italics, the volume and issue, the year, the page range, and a DOI or URL when available.
Bibliography: Jones, Maria. “Patterns in Academic Writing.” Journal of Writing Studies 12, no. 3 (2021): 210–235. https://doi.org/10.xxxx/xxxxx.
First footnote: 1. Maria Jones, “Patterns in Academic Writing,” Journal of Writing Studies 12, no. 3 (2021): 220.
In the footnote, the page number you cite (220) is the exact page used. In the bibliography you give the full page range (210–235). For more detail on this source type, see our guide on how to cite a journal article.
The Author-Date system
The Author-Date system replaces footnotes with short parenthetical citations placed directly in your sentences. Each citation gives the author’s last name and the year of publication, with a page number when you quote or refer to a specific passage. Every parenthetical points to a full entry in a reference list at the end.
In-text citation and reference list entry
Reference list: Smith, John. 2020. The History of Citation. Chicago: University of Chicago Press.
In-text: (Smith 2020, 45).
Two features distinguish Author-Date from NB. First, the year moves to the front of the reference entry, right after the author’s name. Second, there is no comma between the author and the year inside the parentheses: it is (Smith 2020), not (Smith, 2020). The comma appears only before a page number.
A journal article in Author-Date
Reference list: Jones, Maria. 2021. “Patterns in Academic Writing.” Journal of Writing Studies 12 (3): 210–235. https://doi.org/10.xxxx/xxxxx.
In-text: (Jones 2021, 220).
You can also use the author’s name in the sentence (a narrative citation), in which case only the year and page go in parentheses: Jones (2021, 220) argues that writing patterns shift over time. If you want a deeper look at this distinction, our article on parenthetical vs. narrative citations may help.
When to use each system
The choice is rarely yours to make from scratch. Follow the requirement set by your discipline, assignment, or publisher. As a general guide:
- Choose Notes and Bibliography for history, art history, literature, philosophy, and theology, or whenever your sources are varied and you want room to add commentary inside notes.
- Choose Author-Date for the physical, natural, and social sciences, or whenever brevity and quick date visibility matter.
Do not mix the two systems in one paper. If you are deciding between Chicago and other styles entirely, our overview of citation styles explained compares the major options side by side.
How to cite common sources in Chicago style
The structure stays consistent across source types: author, title, container (such as a website or journal), publication facts, and a locator. Below are two frequent cases.
A website
Bibliography: Brown, Lisa. “Understanding Citation Basics.” Citation Help. Last modified March 4, 2022. https://www.example.com/citation-basics.
Footnote: 1. Lisa Brown, “Understanding Citation Basics,” Citation Help, last modified March 4, 2022, https://www.example.com/citation-basics.
For more variations, including pages with no author or date, see how to cite a website.
A book chapter
Reference list: Davis, Robert. 2019. “Editing for Clarity.” In The Writing Handbook, edited by Karen White, 88–104. New York: Example Press.
In-text: (Davis 2019, 95).
Whole books follow the simpler pattern shown earlier; our guide on how to cite a book walks through editions, translators, and multiple authors.
Formatting your Chicago paper
Chicago style includes general formatting expectations as well as citation rules. Standard practice is:
- Use a readable font such as 12-point Times New Roman and double-space the main text.
- Add page numbers in the header, usually the top right.
- Single-space each footnote, with a blank line between notes; footnote numbers are full-sized in the note and superscript in the text.
- Title the source list “Bibliography” in the NB system and “References” in the Author-Date system.
- Alphabetize the source list by author surname and use a hanging indent for each entry.
If you are unsure what to call your source list, the difference is explained in works cited vs. bibliography vs. references.
Build accurate Chicago citations automatically
Formatting every footnote and bibliography entry by hand is slow and easy to get wrong. Our free Chicago citation generator builds correctly formatted notes and bibliography entries for books, articles, websites, and more in both systems. You can also explore the main citation tool for other styles, or switch to the Turabian citation generator if your assignment calls for the student version. Whichever method you choose, careful citation is the simplest way to credit your sources and to avoid plagiarism.
Frequently asked questions
What is the difference between Chicago Notes-Bibliography and Author-Date?
Notes-Bibliography uses numbered footnotes or endnotes plus an alphabetized bibliography, and is common in history and the humanities. Author-Date uses short parenthetical citations such as (Smith 2020, 45) plus a reference list, and is common in the sciences. Both come from the same manual; you pick one and use it throughout your paper.
Which edition of Chicago style should I use?
Use the 18th edition (2024) if your instructor or publisher allows it, since it is the most current. The 17th edition (2017) is still widely accepted and the differences for most students are minor. If you are required to follow a specific edition, check your assignment instructions or style sheet first.
Do I still use “Ibid.” in Chicago style?
The 17th and 18th editions discourage “Ibid.” Instead, use a shortened footnote with the author’s last name, a short title, and the page number, for example: Smith, History of Citation, 78. This is clearer for readers and is the current recommended practice.
Is Turabian the same as Chicago style?
Turabian is a student-focused version of Chicago style based on the same manual. It offers the same two systems (Notes-Bibliography and Author-Date) with small adjustments for coursework, such as title pages and class papers rather than published works. If your assignment says Turabian, follow Chicago rules with those minor differences.