Journal Impact Factor

The Journal Impact Factor is defined as all citations to the journal in the current JCR year to items published in the previous two years, divided by the total number of scholarly items (these comprise articles, reviews, and proceedings papers) published in the journal in the previous two years.

Though not a strict mathematical average, the Journal Impact Factor provides a functional approximation of the mean citation rate per citable item.  A Journal Impact Factor of 1.0 means that, on average, the articles published one or two years ago have been cited one time.  A Journal Impact Factor of 2.5 means that, on average, the articles published one or two years ago have been cited two and a half times.  The citing works may be articles published in the same journal.  However, most citing works are from different journals, proceedings, or books indexed in Web of Science Core Collection.