Journal Impact Factors Journal Impact Factor is from Journal Citation Report (JCR), a product of Clarivate. 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 journal impact factor 2023 for a journal would be calculated as follows: A = the number of times articles published in 2024 were cited in indexed journals during 2025 B = the number of articles, reviews, proceedings or notes published in 2024-2025 impact factor 2024 = A/B (note that the impact factor 2024 will be published in 2025, because it could not be calculated until all of the 2025 publications had been received. Journal impact factor year Y will be published in year Y + 1) Impact factor of Nature, Science and Cell journals can be found on their journal websites.
Science Watch provides ranking and impact factor for selective journals. The list is located here: http://www.sciencegateway.org/rank/index.html MIT Biology Hyertextbook Cell Biology Protocols