About ACS Style
ACS Style uses a notational method of referencing when referring to a source of information within the text of a document.
In its simplest form, a number in superscript format placed in the text of the essay, indicates the relevant reference:
The superscript number appears outside the punctuation if the citation applies to a whole sentence or clause. The superscript number may be placed within a sentence if it is logical to do so. See Citing in the Text for more details.
Citations are numbered consecutively in the order in which they appear in the document, including references cited in the text and in non-text content such as tables and figures. Once a source has been cited, the same number is used in all subsequent references.
Each citation corresponds to a numbered reference containing publication information about the source cited in the reference list at the end of the publication, essay, or assignment:
A numbered list of references must be provided at the end of the paper.
The list should be arranged in the order of citation in the text of the publication, assignment or essay, not in alphabetical order.
List only one reference per reference number. Reuse the original number rather than assigning a new number if the same reference is used more than once. For information on how to format your reference list see the Sample Reference List page.
Include a DOI in your reference list entry if one is available. Do not include the protocol in the DOI (http:// or https://).
It is very important that you use correct punctuation and that the order of details in the references is correct.
Author Names: Include up to ten author names in the reference. If there are more than ten authors for a cited source, include the first ten. After the 10th name, place a semicolon followed by “et al.”
List author names in the order they appear in the cited document.
Write author names in the following format, and always end with a full stop:
Surname, Initial/s, Qualifier if present, such as Jr. or II.
Place of publication information is unnecessary for large publishers, such as the American Chemical Society, Cambridge University Press, CRC Press, Elsevier, Oxford University Press, Royal Society of Chemistry, SpringerNature, and Wiley.
If you are not sure whether the publisher is considered large, it is recommended that the place of publication be included.
Include place of publication information for smaller or specialised publishers using the following formats:
- For locations in the US or Canada - give the city and state for US cities or the city and province for Canadian cities. Use the two-letter postal abbreviations for US states or Canadian provinces and territories. The state or province is not needed if the city is considered a major city in the world and would not be confused easily with other cities of the same name (e.g., New York, Boston, Toronto).
- For all other locations - provide the current city and country name in English. The country is unnecessary for major cities (e.g., London, Paris, Rome). Spell out names of countries unless they have standard abbreviations, such as U.K. for United Kingdom.
See Place Names for more.
See Reference List Entries or All Examples for details on how to construct references for specific resources such as books, journals and web pages.
Important Information
Created October 2010; modified June 2019, May 2023, and July 2024.
The American Chemical Society (ACS) Style is used primarily for publications in chemistry and allied sciences.
Please remember to check with your unit co-ordinator or tutor before submitting your assignments, as their style preference may vary from the guidelines presented here.
When using EndNote referencing software, please use the following output style - ACS. For information about EndNote, please see the EndNote Guide.
Acknowledgement
This referencing guide follows the principles and examples in The ACS Guide to Scholarly Communication published by the American Chemical Society (ACS) 2020. Any important concepts not covered by the 2020 guide are taken from the ACS Style Guide: Effective Communication of Scientific Information published by the American Chemical Society (ACS), 3rd edition, 2006.
These publications constitute the authoritative international guide to ACS publication standards and style.