What Is Journal Impact Factor?

The journal impact factor (JIF) is a measure published by Clarivate that reflects the average number of citations received in a given year by items a journal published in the previous two years. It describes a journal as a whole, not the quality of any single article or author.

How it is calculated (in outline)

For a given year, the two-year JIF is the number of citations received in that year to the journal's citable items from the previous two years, divided by the number of citable items published in those two years. Check Clarivate's current definition and which journals are covered, because details change.

Limitations

• Skewed distribution: a few highly cited papers dominate a journal's average.
• Field differences: citation habits and speed vary across specialties, so values cannot be compared across fields.
• Document types: how items are counted can affect the value.
• Gaming and manipulation (for example excessive self-citation) have been documented.
• Not a measure of article quality or individual researchers.

The San Francisco Declaration on Research Assessment (DORA) recommends not using journal-based metrics such as the JIF as a surrogate measure of the quality of individual research articles.

Using it sensibly

Use the JIF as one signal among many, compare only within a field, and consider other information: scope, editorial and peer-review quality, indexing, readership and transparency.

Illustrative example

Invented for teaching. Two journals have impact factors of 3 and 6 in different specialties. The higher number may reflect a field where articles are cited more quickly and often, not that the journal is better. Within one specialty, the comparison is more meaningful but still limited.

Common pitfalls

• Equating a paper's quality with the journal's impact factor.
• Believing "impact factor" claims from unknown sources; verify with the official provider.

Key takeaways

• JIF is a journal-level citation average with major limits.
• Use it cautiously and compare within fields.

This page is general educational information about research methods. It is not medical, legal or regulatory advice; follow your institution's ethics board and your target journal's instructions.