Skip to Main Content

Impact Factors, and other measures of scholarly impact

Adapted from Impact Factors and Citation Analysis, Robert W. Woodruff Library, Emory University; used by permission.

What is Impact Factor

Impact factor (IF) is a measure of the frequency with which the average article in a journal has been cited in a particular year or period, calculated by Clarivate for articles indexed in its Web of Science database. It is used to measure the importance or rank of a journal by calculating the times its articles are cited. As a journal-level metric, it is frequently used as a proxy for the relative importance of a journal within its field; journals with higher impact factor values are given the status of being more important, or carry more prestige in their respective fields, than those with lower values. While frequently used by universities and funding bodies to decide on promotion and research proposals, it has come under attack for distorting good scientific practices.

How Impact Factor is Calculated?

The calculation is based on a two-year period and involves dividing the number of times articles were cited by the number of articles that are citable.

How to find Impact Factors

Impact factors can only be found by using one source, inCites Journal Citation Reports. Not every journal in the world is tracked by this source, so some journals do not have impact factors at all. Watch the videos below to learn how to find Impact Factor or verify that there is no Impact Factor for a specific journal in a specific year.

Controversies with Impact Factor

Impact Factor is not without faults. It is important to understand some of the problems and controversies that surround the development and implementation of Impact Factor. Here are a few to keep in mind:

Recency Bias

  • Impact Factor calculations only factor in the last few years of citations.

Hot Topics

  • Controversial articles that are cited a lot will give the journal a boost in Impact Factor, thus, influencing scholars to pursue "hot" topics.

Cited Frequently

  • Reviews and Front Matter (editorials, letters to the editor, news, obituaries, etc.) that are cited a lot can give a boost in Impact Factor.

Article Quality

  • Impact Factor does not necessarily denote individual article quality, but rather presents a metric of editorial prowess, marketing, and timing. Journals that accept many publications and publish frequently will have higher Impact Factors than those that do not.

Open Access

  • It can be difficult to find Impact Factor for Open Access journals. This can negatively impact the Open Access/Open Science movement that seeks to encourage freely, accessible scientific information because Impact Factor favors traditional publishing methods.

Tenure Processes & Disciplinary Differences

  • Different disciplines have different citation and publishing practices. For example, disciplines that pursue grants and publish guidelines are not accounted for with Impact Factor.
  • Many tenure processes require including Impact Factor, which favors faculty publishing in high Impact Factor journals and pressures them to continue doing so.

Further information

Impact Factor is just one way to measure impact of a journal. You can also measure journal impact using other measures; assess impact of individual researcher's whole outputs; or examine other measurements of individual article impact. Explore the other tabs on this guide and the related USC Libraries guides below for more information.