Getting a manuscript rejected because of citation formatting errors is one of the most preventable setbacks in academic publishing. Studies suggest that up to 40% of references in submitted manuscripts contain errors, and journals following American Chemical Society referencing standards are no exception. Whether you are writing your first chemistry research paper or preparing a multi-author submission for the Journal of the American Chemical Society, understanding ACS citation style is essential for credibility, compliance, and a smoother peer review process.
This guide covers everything you need to format ACS citations correctly — from choosing your in-text citation method to structuring reference lists for every source type you will encounter in the chemical and physical sciences.
What is ACS citation style?
ACS citation style is the referencing system developed by the American Chemical Society for use in chemistry, biochemistry, and related scientific disciplines. It is the required format for all ACS journals — including JACS, Organic Letters, Analytical Chemistry, and more than 60 other publications — and is widely used in university coursework, theses, and dissertations in the physical sciences.
The authoritative reference for ACS formatting is the ACS Guide to Scholarly Communication (formerly the ACS Style Guide), maintained by the American Chemical Society. The guide defines how to cite journal articles, books, patents, datasets, websites, and other sources both in the text and in the reference list.
What makes ACS citation style different from APA or MLA? ACS prioritizes concise, number-based in-text citations that minimize disruption to the reading flow of technical content. Unlike APA's author-date system, ACS primarily uses superscript numbers or italic numbers in parentheses, which is better suited for papers dense with chemical formulas, equations, and data.
Three ACS in-text citation methods
ACS offers three approaches to citing sources within the body of your paper. You must choose one method and use it consistently throughout your manuscript.
Superscript numbers
This is the most widely used method in ACS journals. Sources are numbered sequentially by order of first appearance, and citation numbers appear as superscripts after the relevant text.
Format examples:
After a single-author reference: Brown⁵ discovered the synthetic power of hydroboration.
After a two-author reference: Chen and Brandizzi⁷ summarize the effects of IRE1 on cell vitality.
For three or more authors: Lassig et al.³ made multiple mutations of the protein.
At the end of a sentence: The drug inhibits activation of the pathway.¹⁴
When citing multiple sources at once, combine them with commas or an en dash for consecutive numbers: ³⁻⁵,⁸
Italic numbers in parentheses
This method works identically to superscript numbering, except citation numbers appear as italicized numbers enclosed in parentheses.
Format examples:
After a reference: Brown (5) discovered the synthetic power of hydroboration.
End of sentence: The drug inhibits activation of the pathway. (14)
Author-date
This method is less common in ACS journals but is sometimes used when the publication year is important to the discussion, such as in literature reviews or historical overviews.
Format examples:
Single author: Brown (1961) discovered the synthetic power of hydroboration.
Two authors: Chen and Brandizzi (2013) summarize the effects of IRE1 on cell vitality.
Three or more authors: Lassig et al. (2015) made multiple mutations of the protein.
End of sentence: The discovery of hydroboration was necessary to further the field of synthetic chemistry (Brown, 1961).
Which method should you choose? Check the author guidelines for your target journal. Most ACS journals prefer superscript numbering. If no specific guidance is given, superscript is the safest default for chemistry papers because it keeps the text clean and is the most space-efficient option.
How to format an ACS reference list
The reference list appears at the end of your paper on a new page. How you organize it depends on which in-text citation method you chose:
Superscript or italic numbers: References are listed in numerical order, matching the order they first appear in the text.
Author-date: References are listed alphabetically by the first author's last name.
General formatting rules
Title the section References (left-justified, not centered or bold in most cases).
Single-space all entries.
Do not use hanging indents with numbered systems — instead, indent after the numeral. With author-date, use hanging indents.
If a source is cited more than once, reuse the same number — do not assign a new one.
Do not include live hyperlinks in print submissions. Include DOIs or stable URLs for online sources.
Use Chemical Abstracts Service Source Index (CASSI) abbreviations for journal titles. Single-word journal names like Nature and Science are not abbreviated.
Author name formatting
List authors as: Last name, First initial. Middle initial. Separate multiple authors with semicolons.
One author: Brown, H. C.
Two authors: Chen, Y.; Brandizzi, F.
Multiple authors: List all authors separated by semicolons. Do not use "et al." in the reference list — that abbreviation is only for in-text citations.
ACS citation examples by source type
Below are templates and formatted examples for the most common source types you will encounter in chemistry research. These follow the current ACS Guide to Scholarly Communication standards.
Journal articles
Journal articles are the most frequently cited source type in ACS papers. Getting this format right is critical.
Template:
Author 1; Author 2; Author 3. Title of Article. Journal Abbreviation Year, Volume (Issue), Page numbers. DOI: 10.xxxx/xxxx.
Examples:
Kuchenreuther, J. M.; Britt, R. D.; Swartz, J. R. New Insights into [FeFe] Hydrogenase Activation and Maturase Function. PLoS One 2012, 7 (9), e45850. DOI: 10.1371/journal.pone.0045850.
Takahaski, T. The Fate of Industrial Carbon Dioxide. Science 2004, 305 (5682), 352–353. DOI: 10.1126/science.1100602.
Key details to note:
The journal abbreviation is italicized. Use the CASSI search tool at cassi.cas.org to look up correct abbreviations.
The year is in bold.
The volume number is italicized.
Always include the DOI when available. This is now the preferred identifier for online articles.
Books without editors
Template:
Author 1; Author 2. Book Title, Edition; Publisher: Place of Publication, Year; page numbers.
Example:
Le Couteur, P.; Burreson, J. Napoleon's Buttons: How 17 Molecules Changed History; Jeremy P. Tarcher/Putnam: New York, 2003; pp 32–47.
Book chapters in edited volumes
Template:
Author 1; Author 2. Chapter Title. In Book Title, Edition; Editor 1, Editor 2, Eds.; Series Information; Publisher: Place of Publication, Year; Volume, page numbers.
Example:
Almlof, J.; Gropen, O. Relativistic Effects in Chemistry. In Reviews in Computational Chemistry; Lipkowitz, K. B., Boyd, D. B., Eds.; VCH: New York, 1996; Vol. 8, pp 206–210.
Note that "In" precedes the book title only when you are referencing a specific chapter, not the entire book.
Websites
Template:
Author (if available). Title of Webpage. Title of Website, Date of Publication. URL (accessed YYYY-MM-DD).
Example:
National Institute of Standards and Technology. NIST Chemistry WebBook. NIST, 2023. https://webbook.nist.gov (accessed 2026-01-15).
Theses and dissertations
Template:
Author. Title of Thesis. Level of Thesis, University, Location, Year.
Example:
Chandrakanth, J. S. Effects of Ozone on the Colloidal Stability of Particles Coated with Natural Organic Matter. Ph.D. Dissertation, University of Colorado, Boulder, CO, 1994.
Patents
Template:
Inventor 1; Inventor 2. Title of Patent. Patent Number, Date.
Example:
Walters, D. B.; Giardina, M. A. System and Method for Chemical Analysis. U.S. Patent 7,654,321, February 2, 2010.
Government publications
Template:
Author 1; Author 2. Title of Report; Publication Number; Agency: Place of Publication, Year; page numbers.
Example:
Dey, A. N.; Bloom, B. Summary Health Statistics for United States Children: National Health Interview Survey, 2003; DHHS Publication PHS 2005-1551; U.S. Government Printing Office: Washington, DC, 2005.
AI-generated content
As of 2025, the ACS has updated its guidelines to include citations for AI tools. If you use an AI tool in your research or writing process, cite it in your reference list.
Template:
AI Tool Name (AI Category). Company. URL (accessed YYYY-MM-DD).
Example:
ChatGPT (Large language model). OpenAI. https://chat.openai.com (accessed 2026-02-10).
Always check your journal's specific policy on AI-generated content, as requirements vary across publications.
Common ACS citation mistakes and how to fix them
Even experienced researchers make formatting errors that delay publication. Here are the most frequent mistakes and how to avoid them.
1. Incorrect journal abbreviations
Using full journal names or non-standard abbreviations is one of the most common errors. Always verify abbreviations through the CASSI database maintained by the Chemical Abstracts Service. For example, the Journal of the American Chemical Society should be abbreviated as J. Am. Chem. Soc., not JACS or J. Amer. Chem. Soc.
2. Missing or incorrect DOIs
Digital Object Identifiers are now expected for virtually all journal article citations. A missing DOI makes it harder for reviewers and readers to locate your sources. Use CrossRef's free DOI lookup tool (doi.org) to verify DOIs before submission.
3. Inconsistent in-text citation style
Mixing superscript numbers with author-date citations within the same paper is a common error, especially in multi-author manuscripts where different team members drafted different sections. Establish a citation style at the start of your project and enforce it across all contributors.
4. Using "et al." in the reference list
The abbreviation "et al." should only appear in in-text citations for works with three or more authors. In the reference list, you must list every author by name, regardless of how many there are.
5. Incorrect punctuation between authors
ACS uses semicolons to separate authors, not commas. This is different from APA style, where commas are the standard separator. A quick find-and-replace before submission can catch this error.
6. Omitting access dates for online sources
For websites and other online-only sources, ACS requires an access date in the format (accessed YYYY-MM-DD). This is easy to forget but important for sources that may change over time.
How to use CASSI journal abbreviations correctly
The Chemical Abstracts Service Source Index, known as CASSI, is the official standard for abbreviating journal titles in ACS citations. Using correct CASSI abbreviations signals attention to detail and helps readers identify sources quickly.
Rules for CASSI abbreviations:
Single-word journal titles are never abbreviated: Nature, Science, Cell.
Multi-word titles follow standard CASSI contractions: Journal of the American Chemical Society becomes J. Am. Chem. Soc.
Journals with section designations can be abbreviated further. For example, Acta Crystallographica, Section C: Crystal Structure Communications can be shortened to Acta Crystallogr., Sect. C or even Acta Crystallogr. with the section letter incorporated into the volume designation.
You can look up any journal abbreviation for free at the CASSI search tool: cassi.cas.org.
Managing ACS citations across large research projects
Formatting a reference list for a single paper is manageable. But when you are working across multiple manuscripts, collaborating with co-authors, or building a literature base for a thesis with hundreds of sources, manual citation management becomes a serious time drain.
Research teams in chemistry and related fields often face these challenges:
Version control problems. When multiple authors contribute references, inconsistencies in formatting accumulate quickly. One collaborator may use full journal names while another uses CASSI abbreviations.
Duplicate references. Across multiple papers or chapters, the same source may appear with slightly different formatting, creating confusion during review.
Style switching. If a paper is rejected from one ACS journal and resubmitted to another with different formatting preferences, reformatting every citation manually is tedious and error-prone.
Broken citation chains. When references are managed across disconnected tools — a PDF reader, a shared drive, a spreadsheet tracker — it is easy to lose track of where a particular source was cited and why.
Why reference management tools matter for ACS formatting
Dedicated reference management software eliminates most of these problems by storing your sources in a structured library and auto-generating citations in the correct style. For ACS-heavy researchers, key features to look for include:
Built-in ACS style templates that handle the specific punctuation, author formatting, and journal abbreviation rules automatically.
CASSI-compliant journal abbreviations so you never have to look up an abbreviation manually.
Collaboration features that let co-authors share a unified reference library and ensure everyone cites sources consistently.
One-click style switching to reformat an entire bibliography when moving between journals.
ScholarDock, a research project and reference management platform, is designed specifically for this kind of workflow. ScholarDock keeps all your references in a single structured library connected to your research projects, so every citation is traceable back to its source material, annotations, and the project it belongs to. When your team works in ScholarDock, everyone draws from the same reference collection — which means no more duplicates, no more inconsistent formatting, and no more hunting through email threads for that one paper someone cited three months ago.
ScholarDock's citation tools auto-format references in ACS style (and other major formats), handle CASSI abbreviations, and keep your bibliography synced with your manuscript as you write. If you need to switch from JACS formatting to Organic Letters formatting, ScholarDock regenerates your entire reference list in seconds.
ACS style for special cases
Citing multiple works by the same first author
When using the author-date system and the first author has published multiple works, organize them as follows:
Single-author works first, then two-author works, then multi-author works.
Within each group, list chronologically.
If two works share the same year, add a lowercase letter: (Hamilton, 2004a) and (Hamilton, 2004b).
Citing sources with no author
Start the reference with the title of the article or document. For in-text citations using author-date, use a shortened version of the title in place of the author name.
Citing supplementary information
If you are referencing supplementary materials associated with a journal article, cite the main article and note the supplementary section. There is no separate format for supplementary information — it is considered part of the parent publication.
Citing preprints
With the growing use of preprint servers like ChemRxiv and arXiv, ACS now accepts preprint citations. Format them like journal articles, but use the preprint server name as the "journal" and include the preprint DOI.
Example:
Smith, J. A.; Lee, K. Advances in Green Solvent Extraction Methods. ChemRxiv 2025. DOI: 10.26434/chemrxiv-2025-xxxxx.
Quick-reference checklist for ACS citation formatting
Use this checklist before submitting any manuscript formatted in ACS style:
In-text method is consistent — superscript, italic parentheses, or author-date used throughout, never mixed.
Reference list order matches in-text method — numerical order for superscript/italic; alphabetical for author-date.
All journal titles use CASSI abbreviations — verified at cassi.cas.org.
Author names separated by semicolons — not commas.
All authors listed in reference list — no "et al." in references (only in-text).
DOIs included for all journal articles — verified through CrossRef.
Year is bold, volume is italic for journal articles.
Access dates included for all online sources in (accessed YYYY-MM-DD) format.
Consistent capitalization — article titles in sentence case, book titles in title case and italicized.
No live hyperlinks in print submissions — URLs appear as plain text.
Start organizing your references the right way
Getting ACS citation formatting right is a matter of precision, consistency, and having the right system in place. For a single paper, this guide gives you everything you need to format your references correctly. But if you are managing dozens of sources across multiple projects and co-authors, manual formatting will eventually cost you time and accuracy.
If your research team is tired of scattered PDFs, inconsistent citation styles, and broken reference chains, ScholarDock brings your entire research workflow — sources, projects, and collaborators — into one connected workspace. With built-in ACS citation formatting, shared reference libraries, and project-level organization, ScholarDock helps you spend less time wrestling with style guides and more time doing the research that matters.