ACS Format: Complete Guide to American Chemical Society Style

If you have ever opened a chemistry journal and wondered why every reference looks the same, you are looking at ACS format. The American Chemical Society publishes the style manual that governs how chemists communicate research, from a freshman lab report to a tier-one paper on catalysis.

ACS format is not just a citation style. It dictates how you present data, structure paragraphs, label figures, and even when to use italics for a chemical name. Get it right, and reviewers focus on your science. Get it wrong, and your manuscript ends up in revision purgatory before anyone reads the abstract.

Most students first meet the format in undergraduate coursework, where instructors expect a polished reference list and clean in-text citations. By the time you reach graduate research, ACS style becomes muscle memory. You stop second-guessing whether to italicize in situ and start drafting figure captions in your sleep.

The trouble is that ACS format has evolved across editions of the ACS Style Guide and the newer ACS Guide to Scholarly Communication, so even seasoned researchers get tripped up on small details. This guide walks you through every layer of ACS style — citations, structure, headings, tables, figures, schemes, equations, supporting information, and the typographic details that separate polished from sloppy.

Those six numbers reveal something important. ACS is not a single rigid template. It is a flexible framework with options, and your job is to pick the right ones for your audience.

A thesis committee may want numbered citations. A specific journal may demand author-date. Your instructor might insist on superscript numbers because that is what JACS uses. Knowing the differences saves hours of reformatting later.

Before we dive in, a quick orientation. The ACS Guide to Scholarly Communication replaced the older print ACS Style Guide in 2020 and lives online at pubs.acs.org. The new guide expanded coverage of inclusive language, data sharing, preprints, and ORCID identifiers — topics the print edition barely mentioned.

If your instructor still references the 3rd edition print book, that is fine for most coursework. For journal submissions, always check the journal-specific author guidelines because they sometimes override the general guide.

Now the bones of an ACS paper. The structure has not changed much in fifty years because it works. A reader should be able to scan the abstract, decide if your work is relevant, jump to the figures, and then read the experimental section if they want to reproduce your results.

That predictable architecture is half of what ACS format buys you. Most ACS papers follow the IMRaD framework — Introduction, Methods, Results, and Discussion — with abstract and references bracketing the manuscript.

Communications and letters compress this into a single flowing narrative, but research articles stick to the traditional sections. The eight cards below show the canonical order you will see in nearly every ACS journal.

That eight-section blueprint covers 90 percent of submissions. Some papers add a Supporting Information citation at the end of the experimental section. Others fold acknowledgments into a footnote on the first page.

Different journals also tweak the order — Organic Letters uses a tighter format than Chemical Reviews, for example. Always pull the author guidelines for your target journal before you start drafting.

Headings inside the paper follow a three-level hierarchy. Level 1 headings are bold, sentence case, and stand alone on a line. Level 2 headings are bold italic and also stand alone. Level 3 headings run into the paragraph, are italic, end with a period, and the body text continues on the same line.

Do not use ALL CAPS, underlining, or large font sizes to mark sections. Keep the styling consistent throughout. Reviewers notice inconsistency before they notice the actual science.

Whichever system you choose, a few rules never change. Journal titles are italicized and use ACS-approved abbreviations from the CASSI database.

Year is bolded in the numerical systems but plain in author-date. Volume number is italicized. Issue number is in parentheses and optional if the journal paginates by volume. Page range uses an en dash, not a hyphen.

The DOI ends the entry, preferably as a full https URL. Books, book chapters, theses, patents, conference proceedings, and software citations each have their own slightly different patterns.

The ACS Guide to Scholarly Communication includes 30+ template examples covering everything from a personal communication to a YouTube video. Bookmark that page and refer back when you encounter an unusual source type. Guessing the format almost always produces something a reviewer will flag.

Once you have citations under control, the next battle is data presentation. Figures, tables, and schemes carry the visual weight of a chemistry paper, and ACS format has specific rules for each.

Get these right and a reviewer can interpret your work in 30 seconds. Get them wrong and even good data looks suspicious. Tables in ACS format use horizontal rules above the header row, below the header row, and at the bottom of the table. No vertical lines.

Column headings include units in parentheses or after a slash — Temperature (degrees C) or Concentration / mol L^-1. Numerical data should align on the decimal point. Footnotes use italic lowercase superscript letters (a, b, c) rather than numbers or symbols, because numbers conflict with citation superscripts.

Figures must have descriptive captions starting with Figure 1. in bold, followed by a sentence-form description. Avoid the lazy Figure 1. NMR spectrum. caption — tell the reader what compound, what nucleus, what solvent, and what the key features are.

Schemes are reaction diagrams and follow figure conventions, just with Scheme 1. as the label. Chemical structures inside schemes should be drawn in ChemDraw or a comparable tool at consistent bond lengths and angles. ACS publishes ChemDraw style templates that match the typeface and line weights used in their journals. Use them.

Beyond the big-picture structure, ACS format has a long list of small typographic conventions that separate a polished paper from a sloppy one. These details may seem fussy, but they are the visual grammar of chemistry. Reviewers see them at a glance, and clean typography correlates with careful science.

Italics carry semantic meaning in ACS style. Use italics for variables (k, T, n), Latin abbreviations like in situ, in vivo, via, and vs., stereochemical descriptors (cis, trans, E, Z, R, S), positional prefixes (o-, m-, p-, tert-, sec-), and the names of journals and books.

Do not italicize Greek letters, chemical element symbols, or numerical subscripts. Do not italicize abbreviations like NMR, IR, GC-MS, or HPLC. Mixing italic and roman correctly is one of the quiet markers of a writer who knows the field.

Numbers and units follow SI conventions with a few ACS quirks. Always put a non-breaking space between the value and the unit so they do not separate at line ends. Use exponents rather than negative slashes when possible. Numbers under ten are written as words in prose unless they carry a unit. With units, always use digits.

One area worth dwelling on is supporting information. Modern chemistry papers offload spectra, crystallographic data, computational details, and supplementary tables into a PDF that lives alongside the main article.

ACS format requires you to reference each SI item in the main text — (see Figure S1 in the Supporting Information) — and to provide a separate cover page summarizing what the SI contains. Supporting Information items use the S prefix consistently: Figure S1, Table S2, Scheme S3.

The numbering restarts at 1 inside SI; it does not continue from the main paper. This separation lets a reader skim the main figures without scrolling past 40 pages of spectra.

Another modern addition is the table of contents graphic, or TOC graphic. JACS and most other ACS journals require a small image, roughly 8 cm wide by 4 cm tall, that captures the essence of the paper at a glance. The graphic appears in journal indexes and email alerts, so it functions as a thumbnail advertisement for your work.

A good TOC graphic is uncluttered, uses two or three colors maximum, and tells a story without text-heavy labels. Bad TOC graphics are cropped figures with tiny axis labels that nobody can read. Treat the TOC like an album cover — it sells the song.

Inclusive language is another area where the new ACS Guide to Scholarly Communication made substantial updates. The guide recommends gender-neutral pronouns, avoiding ableist metaphors, and using current names for chemicals.

These are not enforced like citation rules, but they reflect where the field is heading and editors increasingly flag papers that ignore them. A small shift in word choice can age a paper much better in a few years than the alternative.

A quiet but important detail in ACS format is how you treat numbers in tables and figure axes. Significant figures matter. Reporting a kinetic constant as 1.23456 when your instrument only resolves three significant figures is a flag for reviewers because it overstates precision. ACS style asks you to round to a value that matches the measurement uncertainty.

Error bars on plotted data deserve the same care. Always state in the caption whether the bars represent one standard deviation, standard error of the mean, or a 95 percent confidence interval, and whether they come from replicate experiments or a single fit. Two readers can interpret the same plot wildly differently if the error definition is missing from the caption.

Scale bars on microscopy images and crystal structures sometimes get forgotten. ACS journals require an embedded scale bar in any image where size matters, with the bar length labeled directly on the image rather than only in the caption. Editors push back hard on submissions that hide the scale bar in text-only captions.

Citation density is another area where ACS style gives soft guidance rather than a hard rule. A typical research article in JACS carries 30 to 60 references. A review article in Chemical Reviews can pass 300. Over-citing in a short communication is just as suspect as under-citing in a review.

If you find yourself citing five references to support a single uncontroversial fact, trim down to the two most authoritative ones. If you find yourself citing zero references in an introductory paragraph that makes specific historical claims, add the foundational paper.

Reviewers also notice when you cite your own group too heavily relative to the field. A reasonable self-citation rate sits below 25 percent of total references for most research articles. Higher rates trigger questions about whether your work engages with the broader literature or just orbits your own previous output.

Manuscript file format matters more than students expect. ACS journals accept Microsoft Word files as the working format for most submissions, with LaTeX accepted for select computational journals like Journal of Chemical Theory and Computation.

Submit the Word file rather than a PDF unless the journal specifically requests PDF for blind review. Editors need to make tracked-changes edits and a sealed PDF blocks that workflow. Embed all figures inline at submission, in addition to uploading high-resolution versions separately.

File naming conventions sometimes feel trivial, but a clean filename like Smith_Catalysis_ms.docx beats a chaotic one like final_v4_REAL_FINAL_revised.docx in every editorial interaction. Use the corresponding author surname, a short keyword, and a version tag.

The difference between a manuscript that gets desk-rejected and one that reaches peer review is often a single afternoon of formatting cleanup. Walk through your reference list line by line. Check every figure caption. Re-read your abstract aloud. Those three steps catch most of the issues editors flag in the first 24 hours after submission.

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Treat the final pass as an act of respect for the reviewers who will spend hours with your work. Clean formatting earns careful reading.

Cover letters are part of ACS format even though the style guide barely mentions them. A strong cover letter is one page or less, addressed to the editor by name, and states the title, the significance of the work, and why it fits the target journal.

Avoid restating the abstract. Avoid hype words like revolutionary or groundbreaking. Editors read dozens of cover letters per day and develop a fast filter for inflated claims. A calm, specific letter signaling that you have read recent issues of the journal goes further than a maximalist sales pitch.

Suggested reviewer lists are common in ACS submissions. Provide three to five names who are not coauthors, do not share an institution with you, and have published in adjacent areas within the last five years. Suggested reviewers are not guaranteed picks, but a thoughtful list signals you understand the field.

If you remember one thing from this guide, let it be consistency. ACS format gives you choices — three citation systems, multiple acceptable abbreviations, optional issue numbers — but once you make a choice you have to apply it everywhere.

Reviewers can forgive an unusual style decision if it appears throughout the paper. They cannot forgive a manuscript where references one through ten use superscripts and references eleven through fifty use author-date.

The second thing to remember is to read the journal-specific author guidelines before you start drafting. The general ACS Guide to Scholarly Communication covers 90 percent of cases, but individual journals tweak rules around abstract length, figure size, supplementary content, and TOC graphic dimensions.

Five minutes spent on the journal website saves hours of reformatting later. Bookmark the author guidelines page for your target journal and refer back during revision.

Finally, do not treat ACS format as a hurdle. The conventions exist because they make chemistry papers easier to read, navigate, and reproduce. When you bold a level-one heading or italicize in situ, you are doing your reader a favor.

When you include a DOI in every reference, you are making it possible for someone else to build on your work. The format is a tool for clear communication, not a bureaucratic obstacle. Master it once and it stops being something you think about — leaving room for the science to take center stage.