Journal Impact Factor

Journal Impact Factor: IF = citations(X) / articles(X-1, X-2)

The Impact Factor (IF) is the average number of citations that articles from a journal pick up in year X, counting only the papers it ran in the two prior years (X-1 and X-2). Clarivate publishes it once a year in the Journal Citation Reports (JCR), drawing on the Web of Science database. To give a sense of the top of the field: Cancer Cell sits around 280, The Lancet around 202, the New England Journal of Medicine around 167, Nature around 70, Science around 63, and PNAS around 12. So if a journal got 500 citations in 2025 for the 120 articles it published across 2023–2024, that works out to IF = 500/120 ≈ 4.17.

Applications

It shows up in CAPES Qualis classification (Brazil), in deciding where to submit a paper, in hiring and promotion criteria for faculty, in how grants get evaluated, and in what libraries choose to subscribe to.

FAQ

Why is IF criticized? It varies a lot by field, with engineering IFs running well below medicine. A handful of heavily cited papers can drag the whole number up, and editorial policies can game it without much effort. Back in 2012 the DORA Declaration came out against treating IF as the one number that decides the worth of an individual's research.

What are the alternatives? There's the h-index at the researcher level, SJR and SNIP if you want field-normalized figures, CiteScore from Elsevier/Scopus, Eigenfactor, and Altmetric for mentions in social media and the news.

Is a high IF always better? Not really. A niche journal with an IF of 3 might reach your specific community far better than a general one with an IF of 8. Think about who actually reads it, not just the figure on the page.