The databases listed here also provide basic statistics like number of articles published per year, number of citations to the journal each year, and number of references made each year.
Journal Impact Factor
The number of citations made in the current year to articles in the previous 2 years, divided by the total number of citable articles from the previous 2 years.
The number of citations made in the current year to articles in the previous 3 years of the journal, divided by the total number of articles in the previous 3 years of the journal. New metric, released in December, 2016.
5-Year Journal Impact Factor
Citations to articles from the most recent five full years, divided by the total number of articles from the most recent five full years. "How much is this journal being cited during the most recent five full years?"
Journal Immediacy Index
Citations to articles from the current year, divided by the total number of articles from the current year. "How much is this journal being cited during the current year?"
Journal Cited Half-Life
For the current Journal Citation Reports year, the median age of journal articles cited. "What is the duration of citation to articles in this journal?"
Similar to the 5-Year Journal Impact Factor, but weeds out journal self-citations. It also, unlike the Journal Citation Reports impact factor, cuts across both the hard sciences and the social sciences.
Normalized Eigenfactor (new)
Turns the Eigenfactor into a multiplier. A score of 2 is twice as good as a score of 1; a score of 20 is 4 times as good as a score of 5.
The Eigenfactor score divided by the number of articles published in journal. "I know how impactful the journal as a whole is, but what about the average individual article in the journal?"
SJR - SCImago Journal Rank
This metric doesn't consider all citations of equal weight; the prestige of the citing journal is taken into account.
IPP - Impact per Publication
Also known as RIP (raw impact per publication), the IPP is used to calculate SNIP. IPP is number of current-year citations to papers from the previous 3 years, divided by the total number of papers in those 3 previous years.
SNIP - Source-Normalized Impact per Paper
SNIP weights citations based on the number of citations in a field. If there are fewer total citations in a research field, then citations are worth more in that field.
This metric is based on the articles published by a journal over 5 calendar years. h is the largest number of articles that have each been cited h times. A journal with an h5-index of 43 has published, within a 5-year period, 43 articles that each have 43 or more citations.
The Journal Impact Factor was the first metric created for scholarly journals. Eugene Garfield first conceived of the idea of an impact factor in 1955. It is used to determine the impact a particular journal has in a given field of research and also to determine in which journal an author might wish to publish. It is reported each year in Journal Citation Reports.
The Journal Impact Factor was the only metric available for many years. But once the Internet made gathering statistics easier, other metrics were created. The Eigenfactor was the next popular metric, followed by SJR and SNIP. Definitions and links for these are on this page.
Please remember that these metrics provide only part of the story about a journal's utility and reputation. Your librarian can assist you with these metrics and journal evaluation in general.