Journal Impact Factors are used as a measure of the significance of a journal to its field. Journal Citation Reports (JCR), a part of Web of Science by Clarivate (formerly of Thomson Reuters), is the best place to go to determine the impact factor of a journal. These impact factors are calculated and published yearly, usually in June.
Journal Citation Reports (JCR) allows users to evaluate and compare journals using citation data drawn from scholarly and technical journals and conference proceedings indexed in the Science and Social Sciences Citation Indexes. Users with individual accounts need to search at least once every six months to keep the account active.
Other Metrics & Rankings Sources
Eigenfactor (ranks and maps scientific knowledge, FREE e-resource from University of Washington)
