Citation & Referencing

Chicago Manual of Style Format

The Humanize Team · 17 Jun 2026 · 5 min read
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Understanding Chicago Manual of Style Formatting

The Chicago Manual of Style (CMOS) is a widely used citation and style guide, particularly in the humanities and social sciences. It offers two distinct systems for citing sources: the Notes-Bibliography (NB) system and the Author-Date system. Choosing the right system often depends on your field of study or the specific requirements of your professor or publisher.

The Notes-Bibliography (NB) System

This system is common in literature, history, and the arts. It uses footnotes or endnotes to cite sources within the text. A bibliography at the end of the paper lists all cited sources alphabetically.

How it works:

  • In-text citations: When you quote, paraphrase, or refer to information from a source, you place a superscript numeral (e.g., ¹) after the relevant sentence or phrase. This numeral corresponds to a note at the bottom of the page (footnote) or at the end of the document (endnote).
  • Notes: The first time a source is cited, the note provides full publication details. Subsequent citations of the same source use a shortened form.
  • Bibliography: This is an alphabetical list of all sources used in the paper, providing complete publication information for each.

Example of a footnote:

¹ Jane Doe, The History of Everything (New York: Academic Press, 2020), 45.

Example of a subsequent footnote:

² Doe, History of Everything, 112.

Example of a bibliography entry:

Doe, Jane. The History of Everything. New York: Academic Press, 2020.

The Author-Date System

Often preferred in the sciences and social sciences, this system uses parenthetical in-text citations that include the author's last name and the year of publication. A reference list at the end of the paper provides full publication details for all cited sources.

How it works:

  • In-text citations: Parenthetical citations appear in the text, usually at the end of a sentence. They include the author's last name and the year of publication. If a page number is available and relevant, it's also included.
  • Reference list: This is an alphabetical list of all sources cited in the paper, providing complete publication information. It's similar to a bibliography but is specifically for the Author-Date system.

Example of an in-text citation:

(Doe 2020, 45)

Example of a reference list entry:

Doe, Jane. 2020. The History of Everything. New York: Academic Press.

Key Formatting Elements in Chicago Style

Regardless of which system you choose, several key elements require attention when formatting your paper in Chicago style.

Title Page

Chicago style doesn't mandate a specific format for title pages, but it's good practice to include:

  • Your paper's title
  • Your name
  • The course name and number
  • The instructor's name
  • The date

Center these elements on the page, with ample spacing.

Margins and Spacing

  • Margins: Use one-inch margins on all sides (top, bottom, left, right).
  • Spacing: Double-space the entire paper, including block quotations and notes. Do not add extra space between paragraphs.

Headings

Chicago style doesn't prescribe a rigid hierarchy of headings, but you can use them to organize your paper effectively. Common practice involves:

  • First-level headings: Centered, bold, and title-cased.
  • Second-level headings: Left-aligned, bold, and title-cased.
  • Third-level headings: Left-aligned, italicized, and sentence-cased.

Block Quotations

When quoting more than five lines of text, introduce the quotation with a colon or a full sentence. Indent the entire quotation one-half inch from the left margin. Do not use quotation marks. The citation follows the punctuation at the end of the block quotation.

Example:

As Smith argues:

> The implications of this discovery are far-reaching, suggesting a fundamental shift in our understanding of cellular biology. The initial findings, while preliminary, point towards a new paradigm for research in the coming decades. (Smith 2019, 78)

Citations: What to Include

The specific details required in your citations depend on the source type (book, journal article, website, etc.) and the citation system you're using. However, common elements include:

  • Author(s): Last name, First name.
  • Title: Italicized for books and journals, in quotation marks for articles and chapters.
  • Publication Information: Publisher, place of publication, year for books; journal title, volume, issue, year, page numbers for articles.
  • URLs or DOIs: For online sources.

The Bibliography/Reference List

This is crucial for giving credit and allowing readers to find your sources.

  • Alphabetical Order: Entries are arranged alphabetically by the author's last name.
  • Hanging Indent: The first line of each entry is flush left, and subsequent lines are indented one-half inch.
  • Consistency: Maintain a consistent format for all entries of the same type.

Common Source Types and Their Formatting

Let's look at how to format some common source types in Chicago style.

Books

Notes-Bibliography:

¹ John Smith, The Art of Writing (Chicago: University of Chicago Press, 2021), 150.

Smith, John. The Art of Writing. Chicago: University of Chicago Press, 2021.

Author-Date:

(Smith 2021, 150)

Smith, John. 2021. The Art of Writing. Chicago: University of Chicago Press.

Journal Articles

Notes-Bibliography:

² Emily Carter, "Quantum Entanglement in Everyday Life," Journal of Physics 15, no. 2 (2022): 35.

Carter, Emily. "Quantum Entanglement in Everyday Life." Journal of Physics 15, no. 2 (2022): 30–45.

Author-Date:

(Carter 2022, 35)

Carter, Emily. 2022. "Quantum Entanglement in Everyday Life." Journal of Physics 15, no. 2 (2022): 30–45.

Websites

Notes-Bibliography:

³ "Understanding Climate Change," NASA Global Climate Change, accessed November 15, 2023, https://climate.nasa.gov/evidence/.

"Understanding Climate Change." NASA Global Climate Change. Accessed November 15, 2023. https://climate.nasa.gov/evidence/.

Author-Date:

(NASA Global Climate Change n.d.) (If no author or date, use organization and "n.d." for no date)

NASA Global Climate Change. n.d. "Understanding Climate Change." Accessed November 15, 2023. https://climate.nasa.gov/evidence/.

When to Seek Professional Help

Navigating the nuances of Chicago style, especially with complex sources or specific field requirements, can be challenging. If you're struggling to get your citations just right or need to ensure your paper adheres perfectly to CMOS, professional services can be invaluable. EssayGazebo.com offers AI humanization, professional writing, editing, and formatting services that can help you present your work polished and compliant with any style guide.

Final Thoughts on Chicago Style

Mastering Chicago Manual of Style formatting is a skill that benefits students and professionals alike. By understanding the core differences between the Notes-Bibliography and Author-Date systems and paying close attention to details like margins, spacing, and citation accuracy, you can produce a well-organized and credible academic paper. Remember that consistency and clarity are key.

Frequently Asked Questions

What's the main difference between the Notes-Bibliography and Author-Date systems in Chicago style?

The Notes-Bibliography system uses footnotes or endnotes for citations and a bibliography. The Author-Date system uses parenthetical in-text citations and a reference list.

Do I need to indent my block quotations in Chicago style?

Yes, block quotations (over five lines) should be indented one-half inch from the left margin and should not use quotation marks.

How should I format the bibliography or reference list in Chicago style?

Entries should be alphabetized by author's last name, with a hanging indent for each entry, and double-spaced throughout.

What are the standard margin requirements for a Chicago style paper?

Chicago style typically requires one-inch margins on all sides of the document: top, bottom, left, and right.

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