A Guide to ACS Style (American Chemical Society)

You’ve finished your chemistry lab report, but the citation rules are confusing. Do you use numbers or author names? Where does the year go? Is the journal title abbreviated?

Welcome to ACS style. The American Chemical Society (ACS) style is the standard for all chemistry-related fields. It has very specific, unique rules that differ from other citation styles like APA or MLA.

This guide is your foundational resource for ACS style. We will cover the “macro” context (the different citation systems) and the “micro” skills (how to format your in-text citations and reference list).

What is ACS Style?

ACS Style is the citation and formatting guide of the American Chemical Society, as detailed in *The ACS Guide to Scholarly Communication*. It is used for research papers and lab reports in chemistry, biochemistry, and chemical engineering.

The 3 ACS In-Text Citation Systems

Unlike other styles, ACS gives you three choices for in-text citations. You must choose *one* and use it consistently. Your professor or journal will almost always tell you which one to use.

Numbered systems (1 and 2) are most common in ACS journals.

General Paper Formatting (ACS Style)

While many ACS journals have specific two-column templates, the general guidelines for student papers are simple. For a full list of templates, see the official ACS publishing center.

• Font: A standard, readable font like Times New Roman 12pt.
• Margins: 1-inch margins on all sides.
• Spacing: Double-space the entire paper, including the abstract, body text, and references.
• Title Page: Create a separate title page that includes the paper title, author name(s), affiliations (e.g., university), and corresponding author’s contact info.
• Sections: Organize the paper into logical sections, often following the IMRaD structure (Introduction, Methods, Results, Discussion).

How to Format ACS In-Text Citations

You must choose one of the three systems and stick to it.

Option 1 or 2: Numbered Citations (Superscript or Parenthetical)

This is the most common method.

• The first source you cite is 1 (or ¹). The second is 2 (or ²).
• If you cite the first source again later, you re-use the same number 1.
• Multiple Sources: Group citations with commas. Use a hyphen for a range.
  • Example (superscript): …has been widely studied.²˒³˒⁵⁻⁸
  • Example (parenthetical): …has been widely studied (2, 3, 5–8).
• With Author Name: You can also use the author’s name in the text.
  • Example: Smith¹ (or Smith (1)) was the first to report…

Option 3: Author-Date Citations

This system is identical to APA style.

• One Author: (Smith, 2024)
• Two Authors: (Smith & Jones, 2024)
• Three+ Authors: (Smith et al., 2024)
• Narrative: Smith (2024) reported that…

How to Format the “References” List

The format of your reference list depends on the in-text style you chose.

Core Formatting Rules

• Title: Start on a new page. Title it “References” or “Cited References” (centered or flush-left, depending on the journal).
• Order (If Numbered): If you used numbered citations (1, 2, 3), your list must be in numerical order.
• Order (If Author-Date): If you used author-date citations, your list must be in alphabetical order by author’s last name.
• Indentation: Entries are not indented. They are formatted as a numbered or alphabetical list, flush-left.

Common ACS Reference Examples

ACS style is famous for its heavy use of abbreviations and minimal punctuation. Note the two key differences from other styles:

1. Journal titles are abbreviated (e.g., *J. Am. Chem. Soc.*).
2. Article titles are optional. Many ACS journals omit them to save space. (Ask your instructor for their preference).

Journal Article (with DOI)

Book

Chapter in an Edited Book

Website