ACS citation format: how to cite in American Chemical Society style

The current rules are in the ACS Guide to Scholarly Communication [1], which replaced the print ACS Style Guide (3rd edition, 2006) [2]. This guide is part of our citation styles series; for a comparison of list layouts across styles, see how to format a reference list.

ACS style at a glance

What are the three ACS in-text citation options?

ACS allows superscript numbers, italic numbers in parentheses, or author-date citations, and you must use only one of them in a paper [1], [2]. Most ACS journals use superscript numbers; lab courses vary, so check the course handout.

The examples cite Kolb, Finn and Sharpless's 2001 review that named click chemistry [4].

Several sources at once

Author-date details

• One author: (Pauling, 1960).
• Two authors: (Watson and Crick, 1953).
• Three or more: (Kolb et al., 2001).
• Name in the sentence: Kolb et al. (2001) proposed ...
• Two works by the same authors in one year: 2001a, 2001b.

Referring to a reference by number

In numbered ACS text, you can refer to a source directly: "as described in ref 4" or "see refs 2 and 5". ACS writes "ref" in lowercase with no period.

Correct and incorrect in-text citations

ACS reference format for journal articles

A journal reference gives authors (semicolons between them), the article title, the abbreviated journal name in italics, the year in bold, the volume in italics, the issue in parentheses if you include it, the full page range and the DOI [1].

Pattern:

(n) Author, A. A.; Author, B. B.; Author, C. C. Title of Article.
    Abbrev. Journal Year, Volume (Issue), First Page–Last Page. DOI.

In the published style, Abbrev. Journal is italic, Year is bold and Volume is italic.

Examples (real articles):

(1) Kolb, H. C.; Finn, M. G.; Sharpless, K. B. Click Chemistry: Diverse Chemical Function from a Few Good Reactions. Angew. Chem., Int. Ed. 2001, 40 (11), 2004–2021. https://doi.org/10.1002/1521-3773(20010601)40:11<2004::AID-ANIE2004>3.0.CO;2-5.

(2) Watson, J. D.; Crick, F. H. C. Molecular Structure of Nucleic Acids: A Structure for Deoxyribose Nucleic Acid. Nature 1953, 171 (4356), 737–738. https://doi.org/10.1038/171737a0.

Notes on the parts:

• Authors. Surname first, then initials with periods, separated by semicolons. Do not use "and" before the last author. ACS asks you to list all authors; a long list may be shortened with et al. only beyond a set number.
• Title. Title case, no quotation marks, no italics, ending with a period. Some ACS journals leave article titles out; in coursework and theses, include them unless told otherwise.
• Journal. The CASSI abbreviation in italics, then the bold year with no punctuation between them, then a comma.
• Issue. In parentheses after the italic volume, in plain type. The issue is optional in ACS; include it or leave it out consistently.
• Pages. The full range (2004–2021, not 2004–21). For articles with article numbers instead of pages, give the article number.
• DOI. ACS recommends a DOI for every article that has one. You will see it written as a link (https://doi.org/10.xxxx) or as "DOI: 10.xxxx"; follow your journal's form.

Correct and incorrect journal references

How do you abbreviate journal names with CASSI?

Look up the full journal title in CASSI, the Chemical Abstracts Service Source Index, and copy its abbreviation exactly, including periods and commas [3]. CAS provides a free CASSI search tool online. If a title is one word, ACS does not abbreviate it.

Two traps:

• Similar titles. J. Phys. Chem. A, B and C are separate journals. Copy the letter.
• Abbreviations from other styles. NLM abbreviations used in Vancouver and AMA drop all periods (J Am Chem Soc). ACS keeps them.

ACS reference format for books

A book reference gives authors, the italic book title, the edition, then after a semicolon the publisher, a colon and the city, then the year [1].

Pattern:

(n) Author, A. A.; Author, B. B. Book Title, Edition; Publisher:
    City, Year.

Examples (real books):

(3) Pauling, L. The Nature of the Chemical Bond and the Structure of Molecules and Crystals: An Introduction to Modern Structural Chemistry, 3rd ed.; Cornell University Press: Ithaca, NY, 1960.

(4) Clayden, J.; Greeves, N.; Warren, S. Organic Chemistry, 2nd ed.; Oxford University Press: Oxford, 2012.

For a US city, add the state code (Ithaca, NY). For other places, give the city, and the country if the city is not well known.

Chapter in an edited book

Pattern:

(n) Chapter Author, A. A. Chapter Title. In Book Title, Edition;
    Editor, B. B., Ed.; Series Name, Vol. #; Publisher: City,
    Year; pp First Page–Last Page.

Use "Ed." for one editor and "Eds." for several, and "In" before the italic book title. ACS writes "pp" for pages in book references; check your journal's preference.

ACS reference format for websites

A website reference gives the author or organization, the page title, the site name, the URL and, in parentheses, the date you accessed it [1].

Pattern:

(n) Author or Organization. Title of Page. Website Name. URL
    (accessed Month Day, Year).

Example (a real page):

(5) National Center for Biotechnology Information. PubChem Compound Summary for CID 2244, Aspirin. PubChem. https://pubchem.ncbi.nlm.nih.gov/compound/Aspirin (accessed Nov 14, 2026).

Databases such as PubChem, the Cambridge Structural Database and the Protein Data Bank often say how they want to be cited. Follow their wording for the database itself, and cite the original paper for any structure or result you use.

Numbered vs author-date reference lists in ACS

The entries look the same in both systems; only the numbering and the order change [1], [2].

The same two articles as an author-date list:

Kolb, H. C.; Finn, M. G.; Sharpless, K. B. Click Chemistry: Diverse
    Chemical Function from a Few Good Reactions. Angew. Chem., Int.
    Ed. 2001, 40 (11), 2004–2021. https://doi.org/10.1002/...
Watson, J. D.; Crick, F. H. C. Molecular Structure of Nucleic Acids:
    A Structure for Deoxyribose Nucleic Acid. Nature 1953, 171
    (4356), 737–738. https://doi.org/10.1038/171737a0.

(In the published style, the journal is italic, the year bold and the volume italic.)

ACS style in LaTeX

The achemso package on CTAN provides the LaTeX class and BibTeX styles for ACS journals, and formats a .bib file into ACS references with the bold year and italic volume [5]. Check the capitalization of titles in your .bib file, since BibTeX keeps what you give it unless the style changes case.

Common ACS citation mistakes

• Using "and" or commas between authors instead of semicolons.
• Writing the full journal name, or an NLM abbreviation without periods.
• Forgetting the bold year or the italic volume.
• Shortening page ranges (2004–21).
• Superscripts before the period, or italic numbers after it.
• Mixing numbered and author-date citations in one report.
• Citing a website without an access date.

How to cite in ACS style with AI for Research

1. Generate ACS references. Paste a DOI or title into the ACS citation generator to get the reference with the bold year and italic volume. Citations are free on every plan, with no account needed.
2. Convert a list. If your notes are in APA or another style, paste them into the citation formatter. It looks up each line and returns it in ACS, and flags lines it could not match.
3. Order an author-date list. For ACS author-date lists, the reference list sorter sorts by surname under APA rules and finds duplicates. Check the result, since ACS and APA can differ on ties. For numbered lists, keep the order of first citation.
4. Check the sources. The citation checker checks whether each reference resolves to a real record and whether it has been retracted, and paper search finds the DOI for a paper you only half remember.
5. Export. Word and LaTeX export gives you a .docx or a .tex file with a .bib for achemso.

The in-text citation generator covers APA, MLA, Chicago author-date and Harvard, not ACS. Search, citations and the free tools cost nothing; AI writing features use credits, and the Free plan includes 45 credits a month (see pricing). Always check journal abbreviations against CASSI, because source records sometimes carry other abbreviations.

FAQ

What is ACS citation style?

ACS style is the citation style of the American Chemical Society, set out in the ACS Guide to Scholarly Communication. It is used in chemistry and related fields. You cite sources in the text with superscript numbers, italic numbers in parentheses or author and year, and list them at the end under References, with authors separated by semicolons, the year in bold and the volume in italics.

What are the three ways to cite in ACS style?

ACS allows superscript numbers placed after the punctuation (as reported.1), italic numbers in parentheses placed before the punctuation (as reported (1).), or the author's surname and year in parentheses (Kolb et al., 2001). Numbered citations follow the order of first citation; author-date citations go with an alphabetical reference list. Pick one system and use it throughout the paper.

How do you abbreviate journal names in ACS style?

Use the abbreviations in the Chemical Abstracts Service Source Index (CASSI), which CAS offers as a free online search tool. Search the full journal title and copy the abbreviation exactly, with its periods and commas, for example J. Am. Chem. Soc. or Angew. Chem., Int. Ed. Single-word titles such as Nature and Science are not abbreviated. Set the abbreviated name in italics.

How do you cite a website in ACS style?

Give the author or organization if there is one, the title of the page, the name of the website if different, the URL, and the date you accessed it in parentheses. For example: National Center for Biotechnology Information. PubChem Compound Summary for CID 2244, Aspirin. PubChem. followed by the URL and (accessed Nov 14, 2026). Websites change, so the access date is required.

Is ACS style the same as the ACS Style Guide?

The ACS Style Guide (3rd edition, 2006) was the print manual for ACS style. It has been replaced by the ACS Guide to Scholarly Communication, an online guide from the American Chemical Society that covers references along with writing, ethics and publishing. The core reference format is much the same; check the online guide for current details, and follow your journal or course when they differ.

Next steps

• Compare numbered styles: IEEE citation format and CSE citation format.
• Writing a humanities paper instead? See MLA works cited.
• Need APA for another course? Start with the APA reference list.
• Turning a lab report into a paper? Read how to format a paper for a journal.

Sources

1. Banik, G. M.; Baysinger, G.; Kamat, P. V.; Pienta, N., Eds. The ACS Guide to Scholarly Communication; American Chemical Society: Washington, DC, 2020. https://doi.org/10.1021/acsguide.
2. Coghill, A. M.; Garson, L. R., Eds. The ACS Style Guide: Effective Communication of Scientific Information, 3rd ed.; American Chemical Society: Washington, DC; Oxford University Press: Oxford, 2006.
3. CAS. CAS Source Index (CASSI) Search Tool. https://cassi.cas.org/ (accessed Nov 14, 2026).
4. Kolb, H. C.; Finn, M. G.; Sharpless, K. B. Click Chemistry: Diverse Chemical Function from a Few Good Reactions. Angew. Chem., Int. Ed. 2001, 40 (11), 2004–2021. https://doi.org/10.1002/1521-3773(20010601)40:11<2004::AID-ANIE2004>3.0.CO;2-5.
5. CTAN. achemso: Support for submissions to American Chemical Society journals. https://ctan.org/pkg/achemso (accessed Nov 14, 2026).