Journal-level metrics quantify the place of a particular journal within its field. They are only useful for comparing across subject areas if you choose a normalized indicator. Different vendors offer different metrics to facilitate this comparison. These metrics are commonly used in the Health, Science and the Social Science fields, but are unlikely to be relevant for Arts and Humanities. For a detailed introduction to journal metrics, try the Introduction to Research Impact tutorial.
Here are some of the most popular journal-level metrics:
Journal Impact Factors can be found in Clarivate Analytics Journal Citation Reports.
There are two versions of the Journal Impact Factor, or JIF. The choice of which indicator is preferred is discipline-dependent. JIF should not be used to compare journals in different subject areas.
Journal Impact Factor is calculated by dividing all citations to the journal in the current JCR year to items published in the previous two years by the total number of scholarly items (articles, reviews, and proceedings papers) published in the journal in the previous two years. It works best for fast-moving fields.
The 5-year Impact Factor, available from 2007 onward, is the average number of times articles from the journal published in the past five years have been cited in the JCR year. It is best used to compare journals in a field with longer publication times.
Journal Citation Reports calculates Journal Impact Factors automatically. below is an example of how the calculation works.
Calculating 2017 Journal Impact Factor (JIF)
X = the number of times articles published in 2015 and 2016 were cited by indexed journals during 2017
Y = the total number of "citable items" published in 2015 and 2016
X = 100
——— JIF = 5
Y = 20
Eigenfactor scores can be found in Clarivate Analytics Journal Citation Reports.
The Eigenfactor weights citations so that highly-cited journals influence the score more than less-cited journals. It uses a 5-year publication window and removes journal self-citations. The Eigenfactor favours larger journals, and it should not be used to compare journals in different subject areas.
You may also see a Normalized Eigenfactor Score reported. This rescales the Eigenfactor relative to the number of journals included in the Journal Citation Report that year, setting the average score to 1. A journal with a Normalized Eigenfactor Score of 2 is considered twice as influential as the average journal.
CiteScore is available in Scopus via the "Sources" search.
CiteScore is calculated by taking the sum of the number of citations a journal receives in one year to articles published in the previous three years, and dividing by the number of documents that journal published in those same three years. Unlike the Journal Impact Factor, CiteScore includes all document types (not just scholarly items). The three-year window is seen as a compromise between faster- and slower-moving fields. CiteScore should not be used for comparisons across different subject areas.
Source Normalized Impact per Paper is available in Scopus via the "Sources" search..
The Source Normalized Impact per Paper, or SNIP, corrects for differences in citation patterns by weighting the impact of a single citation to reflect the likelihood of citation in that subject area. SNIP can be used for comparison across subject areas.
Scopus calculates SNIP automatically. Below is an example of how it works.
Calculating 2019 Source Normalized Impact per Paper (SNIP)
200 (citations given in 2019 to papers from 2016-18) ÷
50 (number of papers published 2016-18)
= 4 (citation count per paper)
ABC Journal = ———————————————————
3 (citation potential per field)*
SNIP = 1.33
*Calculated based on citations per paper in all journals categorized in the same Scopus defined field.
The SCImago Journal Rank, or SJR, is a weighted ranking that assigns higher value to citations from highly-cited journals as well as journals more closely related in subject matter to the journal under consideration. It should be used for comparison within a subject area.
h5-index and h5-median are available via Google Scholar.
These metrics are similar to an individual author's h-index, but they are applied to a 5-year sample of the journal's articles. H is defined as the largest number N such that at least N articles in that publication were cited at least N times each.
The h5-median is the median number of citations received by the articles that have citation counts at or above the h-index. It helps illustrate the distribution of citations to articles from that journal.
Both these measures are used for comparisons within a subject area. They are more broadly available for arts, humanities, and social sciences than the previously described indicators, but they are not replicable, because Google offers no transparency about what is covered by this search.
Where you publish will affect your research visibility (how much it is read, cited, etc.) Our Identifying Appropriate Journals for Publication guide will give you the knowledge to wisely choose where to publish your work.