The Impact Factor (IF) is a commonly used journal metric that reflects how frequently the "average article" in a journal is cited in a particular year. It is calculated by dividing the number of citations in a given year to articles published in the previous two years by the total number of citable articles published in those two years.

Impact Factors are published annually in the Journal Citation Reports (JCR) by Clarivate Analytics for journals indexed in the Web of Science Core Collection.

The standard calculation is:

Impact Factor = (Citations in Year X to articles published in Years X‑1 and X‑2) ÷ (Total number of citable articles published in Years X‑1 and X‑2).

Citable articles typically include original research and review articles. Editorials and letters are usually excluded.

• Journal Recognition: A higher Impact Factor often suggests that articles in a journal are cited more frequently, which many researchers interpret as influence within a field.
• Journal Quality Proxy: While widely used, the Impact Factor should not be the sole criterion for judging research quality. Different fields have different citation practices.
• Comparisons Within Fields: It is more meaningful to compare Impact Factors within the same discipline because citation behaviour varies by subject area.

• Not all journals have an Impact Factor; only those indexed in Web of Science and listed in JCR receive one.
• A journal's absence of an Impact Factor does not necessarily mean it is low quality, especially for newer journals or those not indexed in JCR.
• Impact Factor is just one of several metrics. Other measures such as CiteScore, h‑index, eigenfactor, and altmetrics offer additional perspectives on influence.

Many institutions and funding bodies consider Impact Factor along with other metrics when evaluating research output, journal selection, or academic performance. However, researchers are encouraged to consider both quantitative and qualitative factors when making decisions.