Impact Factor

Impact Factor

Definition: The Journal Impact Factor is published each year by Thomson Reuters. It is a measure of the number of times an average paper in a particular journal is cited during the preceding two years.

For example:

A = the number of times articles published in a specific journal in 2009 and 2010 were cited by journals during 2011.

B = the total number of 'citable items' published by that journal in 2009 and 2010. ('Citable items' are usually articles, reviews, proceedings, etc.; not editorials or letters-to-the-editor.)

2011 impact factor = A/B.

Actual value is intentionally only displayed for the most recent year. Earlier values are available in the Journal Citation Reports from Thomson Reuters.

Journal Impact Factor
Cites in 2016 to items published in: 2016=851 Number of items published in: 2016=312
 2015=1124 2015=321
Sum: 1975 Sum: 633
Calculation: Cites to recent items       1975
Number of recent items   633   = 3.120

5-Year Impact Factor


Note: A base of five years may be more appropriate for journals in certain fields because the body of citations may not be large enough to make reasonable comparisons, or it may take longer than two years to publish and distribute leading to a longer period before others cite the work.

5-Year Journal Impact Factor
Cites in{2014} to items published in: 2016=851 Number of items published in: 2016=312
2015=1124 2015=321
2014=879 2014=293
2013=1039 2013=297
2012=983 2012=281
Sum: 4876 Sum: 1504
Calculation: Cites to recent items        4876
Number of recent items   1504=3.242


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