Measure of the number of times an average paper in this journal is cited. Copyright Clarivate Analytics.
The Journal Impact Factor is published each year by Clarivate Analytics. It is
a measure of the number of times an average paper in a particular journal is
cited during the preceding two years.
A = the number of times articles published in a specific journal in 2014
and 2015 were cited by journals during 2016.
B = the total number of 'citable items' published by that journal in 2014 and 2015. ('Citable items' are usually articles, reviews, proceedings, etc.; not editorials or letters-to-the-editor.)
2016 impact factor = A/B.
Actual value is intentionally only displayed for the most recent year. Earlier values are available in the Journal Citation Reports from Clarivate Analytics
Journals are often ranked by Impact Factor in an appropriate Clarivate Analytics subject category. As there are now two Impact Factors published – two-year and five-year Impact Factors – this rank may differ, so care is needed when assessing these ranked lists to understand which of the two metrics is being used. In addition, journals can be categorized in multiple subject categories, giving them different ranks for each subject. Consequently, a rank should always be in context to the subject category.