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Calculation

In any given year, the CiteScore of a journal is the number of citations, received in that year and in previous three years, for documents published in the journal during the total period (four years), divided by the total number of published documents (articles, reviews, conference papers, book chapters, and data papers) in the journal during the same four-year period:³

CS y = Citations y + Citations y − 1 + Citations y − 2 + Citations y − 3 Publications y + Publications y − 1 + Publications y − 2 + Publications y − 3 {\displaystyle {\text{CS}}_{y}={{\text{Citations}}_{y}+{\text{Citations}}_{y-1}+{\text{Citations}}_{y-2}+{\text{Citations}}_{y-3} \over {\text{Publications}}_{y}+{\text{Publications}}_{y-1}+{\text{Publications}}_{y-2}+{\text{Publications}}_{y-3}}}

For example, Nature had a CiteScore 2021 of 70.2:⁴

CS 2021 = Citations 2021 + Citations 2020 + Citations 2019 + Citations 2018 Publications 2021 + Publications 2020 + Publications 2019 + Publications 2018 = 338611 4823 = 70.2 {\displaystyle {\text{CS}}_{2021}={{\text{Citations}}_{2021}+{\text{Citations}}_{2020}+{\text{Citations}}_{2019}+{\text{Citations}}_{2018} \over {\text{Publications}}_{2021}+{\text{Publications}}_{2020}+{\text{Publications}}_{2019}+{\text{Publications}}_{2018}}={338611 \over 4823}=70.2}

For example, the 2017 CiteScores were reported first in 2018 when all data was available completely. CiteScores are typically released in late May,⁵ approximately one month earlier than the JCR impact factors.⁶ Scopus also provides the projected CiteScores for the next year, which are updated every month.⁷

Pre-2020 formula

Before 2020, the score was calculated differently: in a given year, the CiteScore of a journal was the number of citations received in that year of articles published in that journal during the three preceding years, divided by the total number of "citable items" published in that journal during the three preceding years:⁸

CS y = Citations y Publications y − 1 + Publications y − 2 + Publications y − 3 {\displaystyle {\text{CS}}_{y}={{\text{Citations}}_{y} \over {\text{Publications}}_{y-1}+{\text{Publications}}_{y-2}+{\text{Publications}}_{y-3}}}

For example, Nature had a CiteScore of 14.456 in 2017:

CS 2017 = Citations 2017 Publications 2016 + Publications 2015 + Publications 2014 = 114639 7860 = 14.59 {\displaystyle {\text{CS}}_{2017}={{\text{Citations}}_{2017} \over {\text{Publications}}_{2016}+{\text{Publications}}_{2015}+{\text{Publications}}_{2014}}={114639 \over 7860}=14.59}

Because the calculation method changed, knowing the calculation date is an important detail when comparing CiteScores. For example, the Nature CiteScore for 2017 calculated with the post-2020 method is 53.7.⁹

Comparison to JCR Impact Factor

CiteScore was designed to compete with the two-year JCR impact factor, which is currently the most widely used journal metric.¹⁰¹¹ Their main differences are as follows:¹²

Another difference is the definition of the "number of publications" or "citable items".¹³

References

1. "How are CiteScore metrics used in Scopus?". Scopus: Access and use Support Center. 2022-07-29. Retrieved 2023-05-24. https://service.elsevier.com/app/answers/detail/a_id/14880/supporthub/scopus/ ↩

2. Straumsheim, Carl. "How to Measure Impact". Inside Higher Ed. Retrieved 2023-08-13. https://www.insidehighered.com/news/2016/12/14/exploring-citescore-elseviers-new-journal-impact-metrics ↩

3. "Journal Metrics - FAQs". Scopus. Elsevier. Archived from the original on 2020-04-14. Retrieved 2023-02-05. https://web.archive.org/web/20200414230825/https://journalmetrics.scopus.com/index.php/Faqs ↩

4. "Source Details: Nature". Scopus. Elsevier. Retrieved 2023-02-05. https://www.scopus.com/sourceid/21206 ↩

5. "Elsevier releases 2017 CiteScore™ values" (Press release). Amsterdam: Elsevier. May 31, 2018. https://www.elsevier.com/about/press-releases/science-and-technology/elsevier-releases-2017-citescore-values ↩

6. Collier, Keith (June 30, 2021). "The 2021 Journal Citation Reports: A continuing evolution in journal intelligence". Clarivate. https://clarivate.com/blog/the-2021-journal-citation-reports-a-continuing-evolution-in-journal-intelligence/ ↩

7. "Journal Metrics - FAQs". Scopus. Elsevier. Archived from the original on 2020-04-14. Retrieved 2023-02-05. https://web.archive.org/web/20200414230825/https://journalmetrics.scopus.com/index.php/Faqs ↩

8. "Journal Metrics - FAQs". Scopus. Elsevier. Archived from the original on 2020-04-14. Retrieved 2023-02-05. https://web.archive.org/web/20200414230825/https://journalmetrics.scopus.com/index.php/Faqs ↩

9. "Source Details: Nature". Scopus. Elsevier. Retrieved 2023-02-05. https://www.scopus.com/sourceid/21206 ↩

10. Gray, Edward; Hodkinson, Sarah Z. (2008). "Comparison of Journal Citation Reports and Scopus Impact Factors for Ecology and Environmental Sciences Journals". Issues in Science and Technology Librarianship (54). doi:10.5062/F4FF3Q9G. https://journals.library.ualberta.ca/istl/index.php/istl/article/view/2451 ↩

11. "Journal Citation Reports: JCR ®". The University of Notre Dame Australia. Archived from the original on 2021-02-25. Retrieved 2023-02-05. https://web.archive.org/web/20210225045749/https://library.nd.edu.au/researchers/journalrankings/jcrs ↩

12. Van Noorden, Richard (2016). "Controversial impact factor gets a heavyweight rival". Nature. 540 (7633): 325–326. Bibcode:2016Natur.540..325V. doi:10.1038/nature.2016.21131. PMID 27974784. https://doi.org/10.1038%2Fnature.2016.21131 ↩

13. Van Noorden, Richard (2016). "Controversial impact factor gets a heavyweight rival". Nature. 540 (7633): 325–326. Bibcode:2016Natur.540..325V. doi:10.1038/nature.2016.21131. PMID 27974784. https://doi.org/10.1038%2Fnature.2016.21131 ↩