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Impact Factors

Understanding the Journal Impact Factor and the Author Impact Factor.

Journal Impact Factor

Journal Impact Factor is frequently used as a proxy for the importance of a journal to its field. Journal Citation Reports, Eigenfactor and SCImago Journal & Country Rank are tools for finding the impact of a journal or groups of journals.

Journal Citation Reports (JCR)

The JCR provides quantitative tools for ranking, evaluating, categorizing, and comparing journals. The impact factor is one of these; it is a measure of the frequency with which the "average article" in a journal has been cited in a particular year or period. [Garfield, 2005] Journal impact factor applies only to a journal or groups of journals, but not to individual articles or individual researchers.

The impact factor of a journal in a particular year is the number of citations received in the current year to articles published in the two preceding years divided by the number of articles published in the same two years. For example, Pediatrics has a 2006 impact factor of 5.012, which means that on average each of its 2004 and 2005 articles was cited 5.012 times in 2006.

Note that Eigenfactor Metrics (Eigenfactor score and Article Influence score) are available in JCR for the years 2007 and later.

How to find the Journal Impact Factor by individual journal title or by subject groupings:


  1. Go to JCR  .
  2. Select a JCR edition year from dropdown list. (leave View a group of journals by Subject Category).
  3. Click Submit button.
  4. Select one or more subject categories (hold down control <ctrl> key while clicking subjects).
  5. Select Journal or Category data sorts. Under View Journal Data, select Impact Factor.
  6. Click Submit button.

Individual Journal Title:

  1. Go to JCR  .
  2. Select a JCR edition year from dropdown list.
  3. Click radio button to the left of ‘Search for a specific journal’.
  4. Click Submit button.
  5. Enter journal information by complete title, ISSN, abbreviated journal title, or title word.
  6. Click Search button.

In results table click individual journal title for complete information (e.g., explanations of impact factor, immediacy index, citing and cited half-life)

For more details see:

Eigenfactor Metrics

Eigenfactor ranks and maps scientific knowledge:

  • Ranks journals similar to Google ranking of websites. It uses the structure of the entire network (instead of purely local citation information) to evaluate the importance of each journal.  Journals are rated according to the number of incoming citations, with citations from highly-ranked journals weighted to make a larger contribution to the Eigenfactor than those from poorly-ranked journals.
  • Eigenfactor Metrics consists of the Eigenfactor score and the Article Influence score.
    • Eigenfactor score: a measure of the overall value provided by all of the articles published in a given journal in a year. 
    • Article Influence score: a measure of a journal's prestige based on per article citations and comparable to Impact Factor.
  • Measures journal price as well as citation influence. The Cost-Effectiveness Search orders journals by a measure of the value of the dollar they provide.
  • Ranks scholarly journals as well as newspapers, theses, popular magazines, etc.
  • Adjusts for citation differences across disciplines, allowing for better comparison across research areas.
  • Calculations are based on the citations received over a 5-year period vs. 2 years in JCR.
  • Available free of charge on the web. [, 2009]

How to find the Eigenfactor:

  1. Go to
  2. Search for a single journal name or choose a subject category.
  3. Select a year.
  4. Click Search.

Note: advanced search (searches by Thomson JCR subject categories, publisher, and other fields) is also available.

SCImago Journal & Country Rank (SJR)

SCImago Journal & Country Rank (SJR) is free source that includes the journals and country-scientific indicators developed from Elsevier's Scopus database. It ranks journals and compares journal citation among countries. Journals are assigned to major thematic categories as well as to specific subject categories according to Scopus Classification. 

The SJR (SCImago Journal Rank) indicator expresses the average number of weighted citations received in the selected year by the documents published in the selected journal in the three previous years, --i.e. weighted citations received in year X to documents published in the journal in years X-1, X-2 and X-3. For more information, see Description of SCImago Journal Rank Indicator.

How to find journal rankings in SJR:

  1. Go to SJR and click on Journal Rankings.
  2. Select Subject Area, e.g., Nursing.
  3. Select Subject Category, e.g., Maternity and Midwifery.
  4. Select other categories as needed and click Refresh.