Journal Impact Factors

Journal Impact Factor is from Journal Citation Report (JCR), a product of Thomson ISI (Institute for Scientific Information). JCR provides quantitative tools for evaluating 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 given period of time.

The impact factor for a journal is calculated based on a three-year period, and can be considered to be the average number of times published papers are cited up to two years after publication. For example, the impact factor 2014 for a journal would be calculated as follows:

A = the number of times articles published in 2012-2013 were cited in indexed journals during 2014

B = the number of articles, reviews, proceedings or notes published in 2012-2013

impact factor 2014 = A/B

(note that the impact factor 2013 will be published in 2014, because it could not be calculated until all of the 2013 publications had been received. Impact factor 2014 will be published in 2015)

Impact factor of Nature, Science and Cell journals can be found on their journal websites.


The lists of Impact Factors have been removed from this site due to copy right violations. Science Watch provides ranking and impact factor for selective journals. The list is located here:

MIT Biology Hyertextbook
Cell Biology Protocols