Explanation of Journal Impact Factor
Journal Impact Factor, or JIF, is the most commonly-used metric used to indicate journal quality.
As the formula below shows, JIF is a 3-year calculation based on the total number of citations to articles published in the journal.
JIF is available through Thomson Reuters' Journal Citation Reports.
JIF can be searched by journal name, or browsed by discipline. Journal Rankings discusses these disciplines in more detail.
Explanation of SJR, SNIP, and CiteScore
SJR, or SCImago Journal Ranking, is based on JIF's citation formula, but uses a 5-year citation count and applies an algorithm based on Google's to calculate their index.
SNIP is based on SJR, but is 'flattened' or normalized to more easily allow for direct comparison between separate disciplines.
CiteScore is a newer metric uses JIF's citation formula, but uses a 3-year citation count, and is more directly comparable with JIF, due to the similar methodology.
SJR, SNIP, and CiteScore are based on citation records in Scopus.
SJR, SNIP, and CiteScore are all also available through Scopus (click on "Sources" from the home page), but subject rankings are only available based on CiteScore. (More information about disciplines is available in Journal Rankings.)
Scopus also allows for direct graphical comparisons of journals, as demonstrated to the right. This can be found in any individual journal's record in Scopus by clicking on "Compare sources" in the upper-right corner.
SJR, SNIP, and CiteScore are also available through journalmetrics.com. Subject rankings are available based on SJR, SNIP and CiteScore here.
SJR is also available through SCImago's website, including journal rankings.
Explanation of H5-index and H5-median
The H5-index is created by Google Scholar, and is similar to the h-index explained in Author-level Metrics.
H5-index "It is the largest number h such that h articles published in [the past 5 years] have at least h citations each". Thus, an H5-index of 60 means that that journal has published 60 articles in the previous 5 years that have 60 or more citations each.
H5-median is based on H5-index, but instead measures was the median (or middle) value of citations is for the h number of citations. A journal with an H5-index of 60 and H5-median of 75 means that, of though 60 articles with 60 or more citations, the median of those citation values is 75.
To the right is a chart listing the top 20 English-language journals ranked by the H5-index.
Both the H5-index and H5-median are available in Google Scholar Metrics. Journals can be browsed by discipline (more information about disciplines is available in Journal Rankings) or searched by keyword.
Google Scholar Metrics will only display the top 20 journals for each subject category. Additionally, there is no historical data.