IEEE vs APA vs MLA vs Chicago: which citation style to use

Different disciplines have settled on different citation conventions, and submitting work formatted in the wrong style is a common reason for a desk rejection. This guide explains the four styles you're most likely to encounter — IEEE, APA, MLA, and Chicago — what they look like, when each is used, and how to switch between them. You can format any reference in any of these styles automatically with the free Citation Generator by pasting a DOI, ISBN, or arXiv ID.

IEEE — engineering, computer science, physics

IEEE (Institute of Electrical and Electronics Engineers) is the de facto style for most engineering, computer science, and applied-physics venues. It's a numeric citation system: in-text citations are bracketed numbers in the order sources first appear in the manuscript, and the reference list is numbered to match.

In-text:

The approach in [3] outperforms prior work [1], [2].
Recent surveys [4]–[7] confirm this trend.

Reference list entry:

[1] A. Vaswani et al., "Attention is all you need," in
    Advances in Neural Information Processing Systems,
    vol. 30, 2017, pp. 5998–6008.

Author names use first-initial + middle-initial + surname (A. B. Smith). Journal and conference names are typically abbreviated (e.g., "Trans. Pattern Anal. Mach. Intell." instead of the full name). The IEEE Reference Guide is the canonical source; most CS conferences and journals follow it strictly. Where to expect IEEE: ICCV, NeurIPS, ICML, CVPR, IROS, ICRA, the entire IEEE journal portfolio.

APA — psychology, education, social sciences, nursing

APA (American Psychological Association) is the dominant style across psychology, education, sociology, communication, business, and nursing. The 7th edition (2020) is current. APA is an author–date system: in-text citations name the author and year, and the reference list is alphabetical by surname.

In-text:

The original study (Smith, 2020) showed a 23% effect.
Recent meta-analyses (Doe et al., 2022; Roe, 2023) confirm the effect.
Smith (2020) found a 23% effect.

Reference list entry:

Smith, J. A. (2020). The effect of mindfulness on test anxiety
  in undergraduates. Journal of Educational Psychology, 112(4),
  555–570. https://doi.org/10.1037/edu0000388

Notice the journal name is italicized and the volume number is in italics; the issue number is in parentheses and not italicized. DOIs are written as full URLs in APA 7. "et al." is used for in-text citations of works with three or more authors from the first citation on. APA emphasizes the date because recency matters in fast-moving social-science literatures.

MLA — literature, languages, cultural studies

MLA (Modern Language Association) is the standard across the humanities — literary criticism, linguistics, cultural studies, comparative literature. The 9th edition (2021) is current. MLA is an author–page system: in-text citations name the author and a page number, with no year and no comma between them.

In-text:

The narrator's unreliability is established early (Smith 42).
As Smith argues, "the genre demands ambiguity" (Smith 42).

Works Cited entry:

Smith, Jane. "The Genre Demands Ambiguity: Reading Unreliable
  Narrators." PMLA, vol. 135, no. 3, 2020, pp. 451–467.
  JSTOR, https://www.jstor.org/stable/12345678.

MLA renames the reference list "Works Cited" and uses italics for journal and book titles, quotation marks for article titles. The "container" model (introduced in MLA 8 and continued in MLA 9) is distinctive: every source has one or more nested containers (a journal published in a database, for example). MLA also expects access dates for online sources where no publication date is available.

Chicago — history, classics, some humanities, plus a sciences variant

Chicago Manual of Style is unusual in that it offers two distinct systems, both currently in their 17th edition:

Notes–Bibliography (NB)

The system most often associated with Chicago. Used widely in history, classics, art history, religion, and parts of philosophy. Citations live in footnotes or endnotes, with a separate alphabetized bibliography at the end.

Footnote:
1. Jane Smith, A History of Ambiguity (Chicago: University
   of Chicago Press, 2020), 42–43.

Bibliography:
Smith, Jane. A History of Ambiguity. Chicago: University
  of Chicago Press, 2020.

Author–Date

Chicago's other system is structurally similar to APA: in-text author–date citations and an alphabetical reference list. Used in some social-science and natural-science contexts where the editor wants Chicago house style but APA-style readability.

In-text:
The original argument (Smith 2020, 42) was later revised.

Reference list:
Smith, Jane. 2020. A History of Ambiguity. Chicago:
  University of Chicago Press.

If a venue says "Chicago," it usually means notes–bibliography unless the submission guidelines specify otherwise. Always check.

Quick comparison

Variants and house styles

Many publishers layer modifications on top of these base styles. ACM uses an "ACM Reference Format" that's largely IEEE-numeric but with subtle differences (italicization of titles, treatment of preprints). Nature uses a custom author–year format unrelated to APA. Some humanities journals will say "MLA" but require footnotes anyway. Always check the journal's most recent submission guidelines, not generic tutorials.

How to switch styles

If you're moving a manuscript from one venue to another with a different citation style, three options:

1. Reformatter tool. The Citation Generator takes a DOI or ISBN and outputs APA, MLA, Chicago, or IEEE — rebuild any single reference in any style.
2. BibLaTeX style swap. If your manuscript is in LaTeX, the cleanest path is to change your \usepackage[style=ieee]{biblatex} declaration to the target style and recompile. No manual reference-list rewriting needed. The BibTeX Validator can verify your .bib entries have the fields the new style requires.
3. Reference manager. Zotero, Mendeley, EndNote, and Paperpile all support multi-style output. Switch the active style and re-insert all citations.

The Citation Generator and BibTeX Builder both run against authoritative APIs (CrossRef for DOIs, arXiv for preprints) — your reference data is never stored or shared. If you're preparing references at submission time, run the whole .bib through the BibTeX Validator to catch missing required fields or hallucinated DOIs before the manuscript leaves your machine.