A number of different types of metrics exist that try to measure the scholarly impact of an entire peer-reviewed journal. Originally created to help libraries decide which journals to collect, they have since been adopted by faculty as a way to show their own impact. The metrics generally use the average number of citations a journal receives over a certain period, although they differ exactly in what counts and the exact equation. It's important to keep in mind that all of these scores just reflect on average how many citations a journal, not a specific article, receives. This page covers just a few types of journal metrics.
Citation practices can vary greatly among the various disciplines, so its important to see how a specific journal does in comparison to other journals in its subject(s) in whichever tool you use. Otherwise, any metric will convey little helpful information to you.
The Journal Impact Factor (JIF) measures the frequency with which articles in a journal are cited. It is calculated by taking the total number of citations in the current year to articles published in the previous 2 years and dividing by the total of number of articles published in the previous 2 years. Only journals in the Web of Science (WoS) set of databases receive a JIF, and only citations from other WoS journals count toward a journal's JIF. About 21,000 journals had a JIF as of Summer 2021.
Many journals will post their JIF on their website, but you can also find and verify a journal's JIF by going to the Journal Citation Reports database. You can also use this database to explore a journal's ranking in comparison with other journals in its discipline. You can also browse JCR to look at all journals with a JIF in a particular discipline by selecting "Browse by Journals."
The JIF aims to be selective and thus includes only a small percentage of all the scholarly journals. However, the JIF uses some criteria, such as English language-only journals, that can perpetuate biases.
The Scimago Journal Rank (SJR) takes into account both the number of citations and the prestige of the journals from which the citations come over the course of 3-year period. An alternative to the Journal Impact Factor, the SJR is based on any journals in the Scopus database. It is free for anyone to use.
To find a journal's SJR, look for it in the free Scimago database. You can also browse all journals in a subject as well. The Scimago database has a much larger number of journals - about 34,000 - in it than Journal Citation Reports does.
The Eigenfactor Score rates journals on the basis of citations but gives higher weight to those citations coming from more influential journals. Self-citations are not included. The Eigenfactor project was created by professors at the University of Washington and uses data it gathers from Web of Science, meaning it covers the same journals with a Journal Impact Factor.
You can search for specific journals in the Eigenfactor database.