Et al. Rules: How Many Authors to List in Each Citation Style

Multi-author papers are now routine, and papers with twenty or more authors are no longer rare. How many names to list, and when to switch to "et al.", differs by style, and within a style the rule for the reference list is usually different from the rule for in-text citations. Mixing those two rules is one of the most common problems reviewers flag.

Every rule below was rechecked against official sources in September 2026. These numbers change between editions, so the edition is always stated.

Comparison table

Style (edition)	Reference list	In-text citation
APA 7th	Up to 20 authors listed. 21 or more: first 19, ellipsis, final author	One or two names; three or more: first author + et al. from the first citation
MLA 9th	One or two names; three or more: first author + et al.	Same as the list (et al. in parentheses, "and others" in prose)
Chicago 18th	Up to six listed; seven or more: first three + et al.	Notes and author-date: up to two names; three or more: first author + et al.
IEEE Reference Guide	Up to six listed; more than six: first author + et al.	Numbers only; when naming authors in prose, et al. for three or more
Vancouver (NLM, ICMJE)	NLM prefers all authors; ICMJE samples and many journals: first six + et al.	Numeric, so no author-count rule

APA 7th edition

Reference list: list up to 20 authors, with an ampersand before the last. For 21 or more, give the first 19, an ellipsis, and the final author, with no ampersand. APA's own example:

Kalnay, E., Kanamitsu, M., Kistler, R., Collins, W., Deaven, D., Gandin, L., Iredell, M., Saha, S., White, G., Woollen, J., Zhu, Y., Chelliah, M., Ebisuzaki, W., Higgins, W., Janowiak, J., Mo, K. C., Ropelewski, C., Wang, J., Leetmaa, A., . . . Joseph, D. (1996). The NCEP/NCAR 40-year reanalysis project. Bulletin of the American Meteorological Society, 77(3), 437–471.

In-text: one or two authors are always named (Kim & Lee, 2021). Three or more become first author + et al. from the very first citation (Kim et al., 2021). If two different works shorten to the same form, add names until they differ: (Kim, Park, et al., 2021) vs. (Kim, Choi, et al., 2021).

APA 6th edition named three to five authors in the first citation and listed up to seven in references. Some journals still follow the 6th edition, so check which edition the author guidelines cite.

MLA 9th edition

MLA uses the same rule in the list and in the text. One author: Baron, Naomi S. Two authors: Dorris, Michael, and Louise Erdrich. Three or more: Montoya, Maria E., et al. In parentheses write (Montoya et al. 42). The MLA Style Center reserves et al. for the works-cited list and parenthetical citations; in your own sentences write "Montoya and others."

Chicago 18th edition

The 2024 edition simplified the counts. In a bibliography or reference list, list up to six authors; for seven or more, list the first three followed by et al. In notes and author-date citations, name up to two authors; for three or more, give only the first followed by et al. The 17th edition listed up to ten names in the bibliography (seven plus et al. beyond that) and used et al. in notes only for four or more authors, so older templates may be out of date.

IEEE

The IEEE Reference Guide states that IEEE publications must list all authors up to six names; with more than six, use the primary author's name followed by "et al." That means one name, not three. For non-IEEE publications, et al. may be used if the additional names are not provided. In-text citations are numbers, but when you name authors in prose, use et al. for three or more ("Wood et al. [7]").

Vancouver (NLM Citing Medicine and ICMJE)

NLM's Citing Medicine prefers listing all authors, and PubMed records have included every author since 2000. It allows a limit when space is tight. The NLM page of ICMJE sample references says to list the first six authors followed by et al., while noting that NLM now lists all authors:

Rose ME, Huerbin MB, Melick J, Marion DW, Palmer AM, Schiding JK, et al. Regulation of interstitial excitatory amino acid concentrations after cortical contusion injury. Brain Res. 2002;935(1-2):40-6.

In practice, follow the journal: "six then et al." and "three then et al." are both common.

Korean journals

Korean journals mostly adapt APA and set their own numbers. One society's rules use "외" (and others) for three or more authors from the first citation and allow abbreviation in the list only from six authors; another, based on APA 6th, names three to five authors in full at first. "외" and "등" both mean "and others"; pick one and use it consistently.

Writing et al. correctly

The period goes after "al" only: et al. Not "et. al", "et al" or "et.al."
It is not italicized in APA, MLA or Chicago.
At the end of a sentence, use a single period.
The comma before it depends on the style:

Style	Example	Comma before et al.
APA in-text	(Kim et al., 2021)	No (except disambiguation)
MLA list	Montoya, Maria E., et al.	Yes
Chicago list	first three names, et al.	Yes
Chicago note	Kim et al., Short Title	No
IEEE list	J. Yanamadala et al.,	No
Vancouver	Schiding JK, et al.	Yes

Common mistakes

Using the long reference-list rule in the text, or putting "et al." in an APA reference entry (APA lists never use it).
Mixing Chicago 17th and 18th edition counts.
Keeping three names in IEEE, which keeps only the first author.
Trusting an outdated citation-manager style file without checking the output.

The reference generator applies these author-count rules automatically, and the in-text citation generator handles the text side. For the wider picture see how in-text citations work. Your journal's or university's rules always win.