Journal Impact Factor (JIF) is issued by Journal Citation Reports (JCR), which is owned by Clarivate. Inclusion in the JCR is selective - not every journal will have an impact factor assigned. A journal must be in publication for at least three years to receive a JIF. Journal Citation Reports also offers a percentile ranking by field.
"The [Journal] Impact Factor is calculated by dividing the number of citations in the Journal Citation Reports year (the numerator) by the total number of citable items published in the two previous years (the denominator).
Example: The 2021 Journal Citation Reports equation reads: Cites in 2020 to items published in 2018 and 2019."
Please see the documentation for more details.
Journal Normalized Citation Impact (JNCI) is issued by InCites, which is owned by Clarivate.
"The Journal Normalized Citation Impact of a single publication is the ratio of the actual number of citing items to the average citation rate of publications in the same journal in the same year and with the same document type."
Please see the documentation for more details.
Citescore is issued by Scopus, which is owned by Elsevier. It covers more titles compared to Journal Impact Factor (JIF). Unlike the JIF which calculates scores over a 3-year period, Citescore uses a 4-year period. Citescore also offers the Citescore percentile, which indicates the relative position of a journal in its field.
"CiteScore 2024 counts the citations received in 2021-2024 to articles, reviews, conference papers, book chapters and data papers published in 2021-2024, and divides this by the number of publications published in 2021-2024."
Please see the documentation for more details.
Source Normalized Impact Factor (SNIP) is issued by Scopus, which is owned by Elsevier. The SNIP accounts for different citation behaviors between subjects.
"[Compares] each journal’s citations per publication with the citation potential of its field, defined as the set of publications citing that journal. SNIP therefore measures contextual citation impact and enables direct comparison of journals in different subject fields, since the value of a single citation is greater for journals in fields where citations are less likely, and vice versa. SNIP is calculated annually from Scopus data."
Please see the documentation for more details.
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