Bibliometrics and Impact Factor: Journal Citation Reports

This guide explains how impact factor is used and calculated in journal and article rankings, as well as other methods of citation analysis.


Eigenfactor and Article Influence scores are freely available at

The Impact Factor is only available through a paid subscription to Journal Citation Reports (JCR) from Thomson Reuters. JCR also contains the Eigenfactor and Article Influence scores.

Caveats to JCR

You should not depend solely on citation data in your journal evaluations. Citation data are not meant to replace informed peer review. Careful attention should be paid to the many conditions that can influence citation rates such as language, journal history and format, publication schedule, and subject specialty.

You should also consider the following four conditions, which may affect journal's ranking and Impact Factor:

  • impact factor by article type
  • changes in journal format
  • title changes
  • cited-only journals (not covered in Thomson ISI)

More information

Most of the journals in Thomson ISI are English-language from North America, Western Europe and Australia.

Review journals and original research journals are treated the same even though the citation patterns of these types of articles differ.

What is Journal Citation Reports?

The Journal Citation Reports (JCR) database is a unique and comprehensive tool providing bibliometric analysis of more than 5,900 journals in the areas of science and technology and of 1,700 journals in the social sciences. Coverage is international and includes journals published by over 3,300 publishers in 60 countries.

Journals in the Information Science and Library Science category. (Access requires a subscription)

The aim of the JCR is to provide a systematic and objective means of determining the relative importance of science and social sciences journals within their subject categories. Information for each title includes the "impact factor" (measurement of the frequency with which the average article has been cited in a particular year) and the "immediacy index" (how quickly the average article in a journal is cited). The JCR can show you the:

  • highest impact journals
  • most frequently used journals
  • hottest journals
  • largest journals

JCR uses Thomson Reuters (ISI Web of Knowledge) citation data.

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