Journal impact metrics attempt to quantify the importance of a particular journal in its field, usually via an algorithm that takes into account the number of articles published per year and the number of citations to articles published in that journal. Like author impact measurements, journal impact measures have limitations. Dissatisfaction with existing metrics has contributed to the development of new metrics such that there are now quite a few. While these metrics do tell us something, researchers in a discipline will have the best sense of the top journals in their field.
Boxes on this page include descriptions of the more common journal impact metrics, as well as what tools to use to find the metrics.
Journal Citation Reports via Web of Science
You can access Journal Citation Reports (JCR), a product of Thomson Reuters, via Web of Science (look for the link at the top of the page). Published annually, JCR provides a number of journal impact measurements for journals in the sciences and social sciences. Reported metrics include Impact Factor, 5-year Impact Factor, Immediacy Index, and others. Since 2007, JCR has also included Eigenfactor Metrics.
How to get information and metrics about a journal using the Browse Sources interface.
Google Scholar Metrics
Google Scholar Metrics includes a top 100 list of journals for particular subject fields ranked using their 5-year h-index. You can look at top journals in particular subject categories and sub-categories. The underlying data come from Google Scholar. Sections on Metrics, Coverage, and Inclusion tell you more about how the rankings were derived.
Highlights of Journal Metrics
Journal Impact Factor
Frequency with which the 'average article' in a journal has been cited in a particular year or other defined time period using data from Journal Citation Reports.
The 'classic' Impact Factor uses a 2-year citation window, but a 5-year Impact Factor is also available.
Cannot be used to compare journals across disciplines.
Eigenfactor: Measurement of the 'importance' or 'influence' of a journal. Citations from high-quality journals are weighted more than citations from lesser known journals.
Article Influence: Calculated by dividing the Eigenfactor by the number of articles published in the journal.
Both scores use a 5-year citation window, use data from Journal Citation Reports, and are meant to adjust for citation differences across disciplines, since different disciplines have different standards for citation and different time scales on which citations occur.
Uses data from Scopus, with a 3-year citation window.
Weighted by the prestige of a journal. Subject field, quality, and reputation of the journal have a direct effect on the value of a citation. SJR also normalizes for differences in citation behavior between subject fields.
The largest number h such that at least h articles in that publication were cited at least h times each. For example, a publication with five articles cited by, respectively, 17, 9, 6, 3, and 2, has an h-index of 3.
Google Scholar Metrics uses the h5-index, which is the h-index for articles published in the last 5 complete years.