Journal Impact Factors (JIFs) are one of the more commonly used journal level metrics. Generated by Clarivate's Journal Citation Reports (JCR), they are typically used in an effort to represent the impact of a journal.
JIFs are a journal level metric.
JIFs are calculated by taking the number of citations in a given year to articles published in the journal within the 2 preceding years, divided by the total number of citable publications published in the journal within the 2 preceding years.
Example: The Journal of Great Examples (JGE) published 20 citable articles in 2018 and 25 citable articles in 2019. These articles received a total of 225 citations in 2020.
JGE's Journal Impact Factor for 2020 would be 225 citations / 45 publications = 5This would mean that articles published in the JGE in 2018 and 2019 were cited an average of 5 times each in 2020.
Note: JIFs are only available for journals indexed in Web of Science. Additionally, JIFs will be based only on citing publications in Web of Science. (i.e., citations from publications that are not in Web of Science will not be factored into JIFs).
For example, The Journal of Excellent Examples (JEE) has a JIF of 3 in 2020. This would mean that articles published in the JGE in 2018 and 2019 were cited an average of 3 times each in 2020.
Finding a journal's JIF in Journal Citation Reports (JCR)
Finding a journal's JIF in Web of Science
Like any impact metric, JIFs have their limitations. Some of these limitations include:
For an overview of JIFs and their limitations, see:
Garfield E. The history and meaning of the journal impact factor. JAMA. 2006;295(1):90-93. doi:10.1001/jama.295.1.90.
Laccourreye O, Maisonneuve H. The impact factor in peril? Eur Ann Otorhinolaryngol Head Neck Dis. 2019;136(1):1-2. doi:10.1016/j.anorl.2018.10.013.
Wouters P, Sugimoto CR, Larivière V, et al. Rethinking impact factors: Better ways to judge a journal. Nature. 2019;569(7758):621-623. doi:10.1038/d41586-019-01643-3.
For a succinct overview of JIFs and their limitations, see:
Journal impact factor. Metrics Toolkit. Accessed April 8, 2022. https://www.metrics-toolkit.org/metrics/journal_impact_factor/
For a look into how JIFs can be gamed, see:
Davis P. The emergence of a citation cartel. The Scholarly Kitchen blog. April 10, 2012. Accessed April 4, 2022. https://scholarlykitchen.sspnet.org/2012/04/10/emergence-of-a-citation-cartel/
Oransky I. Ten journals denied 2020 impact factors because of excessive self-citation or "citation stacking." Retraction Watch blog. June 30, 2021. Accessed April 8, 2022. https://retractionwatch.com/2021/06/30/ten-journals-denied-2020-impact-factors-because-of-excessive-self-citation-or-citation-stacking/
Falagas ME, Alexiou VG. The top-ten in journal impact factor manipulation. Arch Immunol Ther Exp (Warsz). 2008;56(4):223-226. doi:10.1007/s00005-008-0024-5.