ACM Citation Format: How to Cite in ACM Style

ACM citation format uses bracketed numbers in the text, like [1], that point to a reference list sorted alphabetically by the first author's last name. A journal article reference looks like this: full author names in normal order, year, article title in plain sentence case, the journal name abbreviated and italicized, then volume, issue, month and year, pages, and the DOI as a full URL. This guide gives you the exact pattern for every common source type in computer science, the numbering rule that separates ACM from IEEE, and the LaTeX and Word workflows that produce the format automatically.

The official ACM rule

The authority is ACM's own Citation Style and Reference Formats page (acm.org/publications/authors/reference-formatting), together with the ACM master article templates. ACM does not publish a numbered edition of its style the way APA or MLA do. The spec lives in the author guidelines and, for LaTeX users, in the acmart document class and its ACM-Reference-Format bibliography style, which is why two university handouts can disagree on small details. When a handout and the ACM page conflict, follow the ACM page.

The reference list entry for a paginated journal article follows this pattern:

Format:

Firstname M. Lastname and Firstname M. Lastname. Year. Title of article in sentence case. Abbreviated Journal Name Volume, Issue (Mon. Year), Pages. https://doi.org/10.xxxx/xxxxxxx

ACM's own worked example:

[1] Patricia S. Abril and Robert Plant. 2007. The patent holder's dilemma: Buy, sell, or troll? Commun. ACM 50, 1 (Jan. 2007), 36-44. https://doi.org/10.1145/1188913.1188915

Four details carry the style, and each one is a place where a reference formatted from memory drifts into almost-ACM:

• Author names run in normal order, first name first, and ACM prefers the full first name over an initial when the publication shows it. Two authors are joined with "and" written out. Three or more take commas, with "and" still spelled out before the final name.
• The article title is plain text in sentence case. Only the first word of the title and of the subtitle are capitalized. No quotation marks, no italics.
• The journal name is italicized and usually abbreviated (Commun. ACM, J. ACM, ACM Trans. Web). No punctuation sits between the journal name and the volume number.
• The date goes in parentheses after the issue number, with the month abbreviated: (Jan. 2007). A comma follows the closing parenthesis, then the page range with no "p." or "pp." prefix.

The DOI closes the entry as a full clickable URL in the https://doi.org/ form. If an article genuinely has no DOI, a stable permalink from the publisher or database can stand in; the address bar URL of your library proxy cannot.

How the numbering works (this is the part people get wrong)

ACM references are listed alphabetically by the first author's last name, then numbered in that order. The numbers in your text follow the alphabet, not the order in which you cite. If your first citation is to Zhang and your second to Abril, Abril is [1] and Zhang comes later in the list.

This is the exact opposite of IEEE style, which numbers references in order of first appearance, and it is the single most common cross-contamination error in computer science papers. A student who has written one IEEE paper carries the appearance-order habit into an ACM submission, cites [1] in the first paragraph, and ends up with a reference list that is neither alphabetical nor sequential.

In practice the numbering takes care of itself in LaTeX, because ACM-Reference-Format.bst sorts and numbers the list for you. The rule bites people writing in Word, where adding one new source can renumber most of the list by hand. The section on tooling below covers both workflows.

In-text, the mechanics are simple:

• A citation is a number in square brackets at the point of use: "The complexity of the current patent process dissuades inventors and inhibits innovation [1]."
• Multiple citations share one set of brackets, in ascending order, separated by commas: [1, 15].
• If you name the author in the sentence, give the year in brackets instead of the number: "According to Constantinou [2016], lattice QCD simulations now run at physical quark masses."
• For three or more authors in a narrative citation, name the first author followed by et al.: "Cohen et al. [2007] showed that the problem is decidable."

One scope note before you commit to numbered citations: SIGGRAPH and SIGPLAN venues use an author-date style rather than the numbered one. The acmart class switches between them with \citestyle{acmauthoryear} and \citestyle{acmnumeric}. Check your venue's call for papers; the class default is numeric, and most ACM journals and conferences use it. For a deeper treatment of parenthetical and narrative citation mechanics across styles, see our complete guide to in-text citations.

Worked examples

Every example below comes from ACM's published reference samples or follows them element by element.

1. Journal article (paginated)

[1] Patricia S. Abril and Robert Plant. 2007. The patent holder's dilemma: Buy, sell, or troll? Commun. ACM 50, 1 (Jan. 2007), 36-44. https://doi.org/10.1145/1188913.1188915

The journal abbreviation is italicized in the rendered reference. In-text: [1], or "Abril and Plant [2007]" narratively.

2. Journal article with an article number

Many ACM journals stopped paginating issues continuously and assign each paper an article number instead. The reference swaps the page range for the article number and a page count:

[2] Sarah Cohen, Werner Nutt, and Yehoshua Sagiv. 2007. Deciding equivalences among conjunctive aggregate queries. J. ACM 54, 2, Article 5 (April 2007), 50 pages. https://doi.org/10.1145/1219092.1219093

Note the comma after the issue number, the capitalized "Article", and "50 pages" in place of a range. If you are exporting from the ACM Digital Library, the export already makes this distinction for you.

3. Conference paper

[3] Sten Andler. 1979. Predicate path expressions. In Proceedings of the 6th ACM SIGACT-SIGPLAN Symposium on Principles of Programming Languages (POPL '79), January 29 - 31, 1979, San Antonio, Texas. ACM Inc., New York, NY, 226-236. https://doi.org/10.1145/567752.567774

The proceedings title is italicized, with the venue's short name in parentheses (POPL '79). Two locations appear and they mean different things: San Antonio is where the conference met (state spelled out), New York is where the publisher is (two-letter abbreviation). References exported from the ACM Digital Library render the same elements with the publisher's full name, "Association for Computing Machinery, New York, NY, USA"; both forms are in circulation and both trace back to ACM's own output. Conference papers dominate publishing in computer science, so if you write in this field this is the pattern to memorize. It differs from the IEEE conference paper format in nearly every element.

4. Book

[4] David Kosiur. 2001. Understanding Policy-Based Networking (2nd. ed.). Wiley, New York, NY.

The book title is italicized and keeps Title Case. The edition goes in parentheses, and ACM's rendering puts a period after the ordinal as well as after "ed.": (2nd. ed.). That double period looks like a typo. It is not; it is what the style produces, and "correcting" it is a real mistake markers notice in the other direction.

5. Edited collection

[5] David Harel (Ed.). 1979. First order dynamic logic (1st. ed.). Lecture Notes in Computer Science, Vol. 68. Springer-Verlag, Berlin. https://doi.org/10.1007/3-540-09237-4

The editor's name comes first with "(Ed.)" after it. The series name stays in plain text with the volume number after it.

6. arXiv preprint

[6] Martha Constantinou. 2016. New physics searches from nucleon matrix elements in lattice QCD. arXiv:1701.00133. Retrieved from https://arxiv.org/abs/1701.00133

The arXiv identifier is written with no space after the colon, followed by a period, then "Retrieved from" and the abstract page URL. If the paper has since been published in a journal or proceedings, cite the published version instead; the preprint form is for work that exists only on arXiv at the time you cite it.

7. Web page

[7] Harry Thornburg. 2001. Introduction to Bayesian Statistics. (March 2001). Retrieved March 2, 2005 from http://ccrma.stanford.edu/~jos/bayes/bayes.html

Online sources are where ACM requires an access date: "Retrieved" plus the date you read the page, in month day, year format, then "from" and the URL. DOIs never take an access date; URLs do, because the page behind a URL can change.

8. Thesis or dissertation

[8] Kenneth L. Clarkson. 1985. Algorithms for Closest-Point Problems (Computational Geometry). Ph.D. Dissertation. Stanford University, Palo Alto, CA. UMI Order Number: AAT 8506171.

The thesis title is italicized in Title Case, followed by "Ph.D. Dissertation" or "Master's thesis", the institution, and its location. The UMI (ProQuest) order number is included when the thesis is in that database and can be omitted when it is not.

Special cases

No individual author

Substitute the publishing organization for the author. ACM's own site, cited as a whole website:

[9] ACM. 2024. Association for Computing Machinery: Advancing Computing as a Science & Profession. Retrieved February 20, 2024 from http://www.acm.org/

If the page shows no publication date at all, use the copyright year from the site footer.

Technical report

[10] David Harel. 1978. LOGICS of Programs: AXIOMATICS and DESCRIPTIVE POWER. MIT Research Lab Technical Report TR-200. Massachusetts Institute of Technology, Cambridge, MA.

The report title keeps any capitalization from the original, then the report series and number, then the institution. Notice that ACM's own example keeps the report title's all-caps words exactly as the source printed them.

Patent

[11] Solyman Ashrafi. 2020. Unified nonlinear modeling approach for machine learning and artificial intelligence (attractor assisted AI). (Aug. 2020). Patent No. 10755188B2, Filed Oct. 16th., 2018, Issued Aug. 25th., 2020.

The inventor is the author. The filing and issue dates are both given, with the day carrying an ordinal suffix and a period ("16th.,"), another ACM quirk that looks wrong and is not.

Online video

[12] Barack Obama. 2008. A more perfect union. Video. (5 March 2008). Retrieved March 21, 2008 from http://video.google.com/videoplay?docid=6528042696351994555

The word "Video." sits after the title as a format label. The upload date goes in parentheses in day month year form, and the access date follows the usual Retrieved pattern.

Software and code

ACM's sample for a manual or software artifact is minimal: author, year, italicized title, organization ("John Prusky. 1978. FRESS resource manual. Brown University."). For modern software, the defensible move is to follow that skeleton and add the version and a repository URL with an access date, since ACM has no fuller official pattern for a GitHub repository. Whatever you choose, format every software reference in the paper the same way.

ACM vs IEEE: the two numbered styles of computing

Both styles cite with bracketed numbers, which is exactly why they get mixed up. The differences run through every element:

If your reference list is alphabetical but your titles are in quotation marks, or your numbers follow appearance order under full author names, you have written a hybrid that fails both specs. Pick the style your venue asks for and let every element follow it.

Getting the format from your tools

LaTeX. Use the acmart class with BibTeX and the bundled style: \bibliographystyle{ACM-Reference-Format}. The class handles the alphabetical sorting, the numbering, the italics, and the sentence-casing of titles. Because BibTeX lowercases titles for you, wrap anything that must stay capitalized in braces in your .bib file: title = {Verifying {TLA+} specifications}. Page ranges in the .bib file take a double hyphen (226--236), which renders as the en dash ACM prints. The class is actively maintained on GitHub (borisveytsman/acmart) and ships with every major TeX distribution, so update your distribution before fighting a formatting bug that may already be fixed.

Word. ACM's Word workflow uses the master article template with paragraph styles, and its submission checker flags reference problems such as citations out of order for author-date venues. Word will not renumber bracketed citations for you. If you manage references by hand, write the paper citing author names as placeholders, alphabetize the finished list once, then assign numbers and replace the placeholders in a single pass at the end. Doing it incrementally is how lists end up with two [7]s.

Reference managers. Zotero and Mendeley both carry a CSL style named "ACM SIG Proceedings" or similar. These get you close, and they are fine for coursework, but CSL cannot reproduce every detail of the BibTeX output (the "(2nd. ed.)" rendering, some abbreviation choices), so for a camera-ready ACM submission the acmart BibTeX route is the one that matches what the publisher expects.

Common mistakes and how to avoid them

• Numbering by order of appearance. The IEEE habit. ACM sorts alphabetically first, then numbers. If your [1] is not the alphabetically first author in the list, the list is in the wrong order.
• Inverting author names. "Abril, Patricia S." is APA and MLA muscle memory. ACM writes names in normal reading order.
• Reducing first names to initials. IEEE muscle memory this time. ACM prints the full first name when the source shows it.
• Title Case in article titles. Article and paper titles take sentence case. Book and thesis titles keep Title Case and italics. Applying either rule to the other source type is the most visible error in a hand-built list.
• Putting the article title in quotation marks. No ACM reference type uses them. Quotation marks around a title mean the writer is thinking in IEEE or Chicago.
• Dropping the DOI or shortening it. ACM wants the full https://doi.org/ URL, and it replaces any need for an access date on that entry.
• Adding access dates to everything. "Retrieved ... from" belongs on web pages and other unarchived URLs. A journal article with a DOI takes no access date.

Quick-reference table