Chicago Style Citations: Notes, Bibliography, and Author-Date

The rules follow The Chicago Manual of Style, 17th edition (2017), with notes on what the 18th edition (2024) changed. Where your instructor’s handout differs from anything below, the handout wins.

The two systems in one table

The year moving from the end of the entry to just after the author is the one visible difference between a bibliography entry and a reference-list entry. Everything else carries over. If you have written in APA, the author-date system will feel familiar; How to Format a Research Paper in APA Style, Step by Step shows the parallel.

Notes-bibliography: the mechanics

A citation in the NB system has three parts, and a complete paper needs all of them.

1. The note number in the text. A superscript Arabic numeral placed at the end of the sentence or clause that uses the source. It goes after periods, commas, and closing quotation marks; it goes before a dash. Numbers run consecutively through the paper (or through each chapter of a thesis) and never repeat, even when you cite the same source again.

Grain prices in the port towns rose faster than in the interior, a pattern the customs ledgers record in detail.¹ The interior towns, by contrast, saw prices flatten after 1740.²

2. The note itself. Footnotes sit at the bottom of the page; endnotes sit in a section before the bibliography. Most instructors prefer footnotes because the reader does not have to flip. The first time you cite a source, the note is complete. Every later citation of that same source uses a shortened note.

1. Adaeze Okafor, Salt Roads: Trade and Weather in the Northern Ports, 1700–1780 (Chicago: Lakeshore University Press, 2021), 112.
2. Okafor, Salt Roads, 140.

The shortened note is surname, a short form of the title (up to about four words), and the page. The 17th edition recommends shortened notes over “ibid.”; if you were taught to use “ibid.”, it is still allowed, but only when the previous note cites the same source and nothing else.

3. The bibliography. An alphabetical list on its own page at the end, titled Bibliography. Entries use a hanging indent, invert the first author’s name, and separate the main elements with periods instead of the commas and parentheses used in notes.

Okafor, Adaeze. Salt Roads: Trade and Weather in the Northern Ports, 1700–1780. Chicago: Lakeshore University Press, 2021.

The same information appears three ways, and only the punctuation changes: notes read like a sentence (commas, parentheses around publication details); bibliography entries read like a list (periods between elements). If you are new to citing sources at all, Citations in Research Papers: A Practical Guide to Crediting Sources explains what a citation has to do before you worry about which style it is in.

Patterns for the common source types

Each pattern below shows the full note (N), the shortened note (S), and the bibliography entry (B). Titles of books and journals are italicized; titles of articles, chapters, and web pages go in quotation marks. Chicago uses headline-style capitalization for titles: capitalize the first and last words and every major word.

Book with one author

N: 1. Tomas Lindqvist, The Quiet Machines: Automation Before Electricity (New York: Harrow & Vale, 2019), 57–58.
S: 2. Lindqvist, Quiet Machines, 61.
B: Lindqvist, Tomas. The Quiet Machines: Automation Before Electricity. New York: Harrow & Vale, 2019.

Book with two or three authors

All names appear, in the order the title page gives them. Only the first name is inverted in the bibliography.

N: 3. Maren Solheim and Priya Raghunathan, Reading the Tide Tables (Boston: Kelp Press, 2020), 14.
S: 4. Solheim and Raghunathan, Tide Tables, 22.
B: Solheim, Maren, and Priya Raghunathan. Reading the Tide Tables. Boston: Kelp Press, 2020.

For four or more authors, the note gives the first author followed by et al.; the 17th edition bibliography lists up to ten names before switching to et al. (see the 18th-edition note below, because this threshold changed).

Chapter in an edited book

Cite the chapter author and title first, then the book, then the editor.

N: 5. Halvard Brenna, "Ice Harvest Contracts," in Cold Commerce: Essays on Northern Trade, ed. Ruth Achterberg (Chicago: Lakeshore University Press, 2018), 203.
S: 6. Brenna, "Ice Harvest Contracts," 210.
B: Brenna, Halvard. "Ice Harvest Contracts." In Cold Commerce: Essays on Northern Trade, edited by Ruth Achterberg, 197–224. Chicago: Lakeshore University Press, 2018.

The bibliography entry includes the full page range of the chapter; the note gives only the page you used.

Journal article

Volume, issue, year, and page follow the journal title. Add the DOI (as a full https link) when the article has one; otherwise a stable URL is acceptable for articles read online.

N: 7. Ines Carvalho, "Weather Diaries as Price Records," Journal of Maritime Economics 44, no. 2 (2022): 131.
S: 8. Carvalho, "Weather Diaries," 135.
B: Carvalho, Ines. "Weather Diaries as Price Records." Journal of Maritime Economics 44, no. 2 (2022): 118–47. https://doi.org/10.0000/jme.2022.44.2.118.

Website or web page

Give the page title, the site name, the date (publication or last modification), and the URL. If no date is available, give an access date instead.

N: 9. "Reading a Customs Ledger," Northern Ports Archive, last modified March 3, 2023, https://www.example.org/ledgers/reading.
S: 10. "Reading a Customs Ledger."
B: Northern Ports Archive. "Reading a Customs Ledger." Last modified March 3, 2023. https://www.example.org/ledgers/reading.

When a web page has a named author, the author goes first, exactly as with a book. When in doubt about whether a minor web source belongs in the bibliography, include it.

Author-date: the same sources, moved around

In the author-date system, the citation sits inside the sentence in parentheses: the author’s surname, the year, and, when you are pointing to a specific passage, the page after a comma. There is no comma between the name and the year.

Grain prices in the port towns rose faster than in the interior (Okafor 2021, 112), while the interior towns saw prices flatten after 1740 (Okafor 2021, 140).

When the author’s name is already in the sentence, only the year and page go in parentheses: Okafor (2021, 112) shows that… Two sources in one citation are separated by a semicolon: (Okafor 2021; Carvalho 2022). Two works by the same author in the same year get letters: 2021a, 2021b, assigned in the order the titles fall alphabetically in the reference list.

The reference list is titled References, and each entry moves the year to sit directly after the author:

Carvalho, Ines. 2022. "Weather Diaries as Price Records." Journal of Maritime Economics 44 (2): 118–47. https://doi.org/10.0000/jme.2022.44.2.118.
Lindqvist, Tomas. 2019. The Quiet Machines: Automation Before Electricity. New York: Harrow & Vale.
Okafor, Adaeze. 2021. Salt Roads: Trade and Weather in the Northern Ports, 1700–1780. Chicago: Lakeshore University Press.

Two small differences from the bibliography form: the journal issue number goes in parentheses after the volume without “no.”, and the year is no longer repeated at the end. Author-date papers can still have footnotes, but only for commentary, not for citations.

Quotations, page numbers, and other details

• Block quotations. Chicago suggests setting off prose quotations of roughly 100 words or more (or several paragraphs) as an indented block without quotation marks, with the note number or parenthetical citation after the final punctuation. For anything shorter, run the quotation into your sentence; How to Use Quotes in an Essay Without Losing Your Own Voice covers how to integrate them.
• Page numbers in notes. Give the page the material appears on. For a source without pages (a web page, an e-book with reflowing text), use a chapter, section heading, or paragraph number, or omit the locator.
• Publisher names. Drop “Inc.”, “Ltd.”, and “Co.”; keep “Press” and “Books” when they are part of the name.
• Same source, several times in one paragraph. In NB, each use gets its own shortened note. Do not put one number at the end of the paragraph to cover everything.

What the 18th edition changed

The Chicago Manual of Style, 18th edition, appeared in 2024. Most citation formats carried over unchanged, and papers written to the 17th edition still look correct to almost every reader. The changes worth knowing about:

• Place of publication is no longer required for books. A 17th-edition entry reads Chicago: Lakeshore University Press, 2021; an 18th-edition entry reads Lakeshore University Press, 2021. Including the city is not treated as an error, so if your instructor’s examples still show it, follow them.
• The author-count threshold for et al. in bibliographies was lowered. The 17th edition listed up to ten authors; the 18th lists fewer before switching to the first three plus et al. If you are citing a source with many authors, check which edition your course follows and copy its example rather than relying on memory.
• Shortened notes remain preferred over “ibid.”, as in the 17th.

When your syllabus does not name an edition, ask, and failing that follow whichever edition your library’s guide uses.

Page setup for a student paper (Turabian)

The Manual is written for publishers and says little about margins. Turabian, its student version, fills that gap:

Common mistakes

1. Repeating the full note. Only the first citation of a source is complete. The second and later citations are shortened. Students who paste the same full note ten times are signaling that they did not read the rule.
2. Mixing the systems. A paper with footnotes and parenthetical (Okafor 2021) citations is using neither system correctly. Choose one.
3. Forgetting the bibliography. Footnotes alone are acceptable only when the assignment says so.
4. Note punctuation in the bibliography. Parentheses around the publisher and commas between elements belong in notes. Bibliography entries use periods.
5. Sentence-case titles. Chicago capitalizes major words in titles. Salt roads: trade and weather is APA style, not Chicago.
6. Numbering by source instead of by occurrence. Note numbers are consecutive through the paper. If the third source you cite is Okafor, its first note is number 3, not number 1.
7. Dropping the page number. A note that cites a whole 400-page book for a single claim does not help the reader find it. Cite the page.

Accidental plagiarism in Chicago-style papers usually comes from mistake 7 combined with paraphrases that drifted too close to the original. Citing Sources Correctly: A Practical Guide to Avoiding Plagiarism works through how to keep paraphrases honest.

Quick checklist before you submit

• Which system does the assignment want, NB or author-date? The paper uses only that one.
• Every superscript number in the text has a matching note, and the numbers run in order with no repeats.
• First citation of each source is a full note; later citations are shortened (surname, short title, page).
• Every source cited in a note or parenthetical appears in the bibliography or reference list, and nothing appears there that was not cited (unless the instructor allows a list of works consulted).
• Bibliography entries are alphabetical by surname, with a hanging indent, first author’s name inverted.
• Book and journal titles are italic; article, chapter, and web page titles are in quotation marks; all use headline-style capitalization.
• Journal entries include volume, issue, year, page range, and a DOI where one exists.
• Page numbers appear in every note that points to a specific passage.
• Edition confirmed: if the instructor follows the 18th edition, the place of publication is optional and the multi-author rules differ.
• Page setup matches Turabian or the course handout.

Frequently asked questions

Do I need both footnotes and a bibliography in Chicago style?

In the notes-bibliography system, most instructors want both: full notes at the bottom of each page and an alphabetical bibliography at the end. Some short assignments allow full notes without a bibliography. In the author-date system there are no citation notes at all; the parenthetical citations point to a reference list, which is required. Ask which system the course uses before you start.

Can I still use “ibid.” in Chicago style?

Yes, but the 17th edition (2017) prefers shortened notes, and the 18th keeps that preference. A shortened note such as “Okafor, Salt Roads, 112.” tells the reader exactly which source you mean even if the previous note is on another page, which “ibid.” cannot do. If your instructor asks for “ibid.”, use it only when the note immediately before cites the same source.

Where does the superscript number go if the sentence ends with a quotation?

After the closing quotation mark and after the period: …“as the ledger shows.”¹ The only punctuation the number goes before is a dash. If a sentence borrows from two sources, place a separate number after the clause each one supports rather than stacking two numbers at the end.

What is the difference between Chicago and Turabian?

Turabian is a version of The Chicago Manual of Style written for students and dissertation writers. The citation formats are the same. Turabian adds page-layout rules that the Manual leaves to publishers: a title page, one-inch margins, double-spaced text with single-spaced notes and bibliography entries, and page numbers. When a course says Chicago, Turabian’s layout rules are usually what it means.