Journal Impact Factor
Journal Impact Factor, a product of Web of Science, is among the best known journal metrics. Calculated for the journals indexed in the Web of Science Core Collection databases, the journal impact factor is the frequency with which an average article from a journal is cited in a particular year. A journal with a higher Impact Factor is often more prestigious than a journal with a lower impact factor. Many journals list their impact factors on their websites. Example. To find a journal's impact factor, search Journal Citation Reports.
More information at the Citation Analysis and Impact Factors guide.