Journal Impact Factor Calculation: Simple Explanation for Editors
Reviewed by the NeucitePress Editorial Board — PhD academics, peer-reviewed journal editors and subject-matter specialists.
Last updated: October 2026 • Reviewed by the NeucitePress Editorial Board • Reading time: 5 minutes
The journal impact factor (JIF) is published each year by Clarivate in the Journal Citation Reports (JCR). It is a simple ratio, and most of the confusion around it comes from what counts in the top and the bottom of that ratio. This guide walks through the calculation with a worked example, explains what editors can and cannot influence, and compares the JIF with other journal metrics.
Key takeaways
- The JIF for a given year is the number of citations received in that year to items published in the previous two years, divided by the number of citable items published in those two years.
- Citable items are articles and reviews. Citations to other item types, such as editorials, can still count in the numerator, which is why article-type mix matters.
- Only journals in Clarivate’s Web of Science Core Collection receive a JIF. A journal’s own figure cannot be calculated from public data alone because Clarivate controls the underlying citation index.
- Compare a JIF only with journals in the same subject category. Citation habits differ widely between fields.
The formula
For a JCR year Y, the impact factor is:
JIF (Y) = citations in Y to items published in Y−1 and Y−2 ÷ citable items published in Y−1 and Y−2
The 2025 JIF, released in the 2026 JCR, therefore counts citations made during 2025 to items the journal published in 2023 and 2024.
A worked example (illustrative figures)
The numbers below are invented to show the arithmetic; they do not describe any real journal.
What counts, and what does not
- Denominator: citable items, which Clarivate defines as research articles and review articles.
- Numerator: citations to any item the journal published in the two-year window, including content that is not counted as citable. Editorials and letters that are widely cited can therefore raise the ratio.
- Timing: which year an article counts for depends on the year of final publication; Clarivate has changed how early access content is assigned, so check the current JCR documentation for edge cases.
- Self-citations: they are included in the calculation, but Clarivate can suppress a journal from the JCR when self-citation or citation stacking distorts its ranking.
How other metrics differ
| Metric | Provider | Citation window | Key feature |
|---|---|---|---|
| Journal Impact Factor | Clarivate (JCR) | 2 years (a 5-year version is also reported) | Ratio of citations to citable items |
| CiteScore | Elsevier (Scopus) | 4 years | Counts citations to all document types published in the window |
| SJR | SCImago (Scopus data) | 3 years | Weights citations by the prestige of the citing journal |
| SNIP | CWTS (Scopus data) | 3 years | Normalises for citation habits in the journal’s field |
Common questions
When does a new journal receive its first impact factor?
Only after it has been selected for the Web of Science Core Collection, which Clarivate decides against its published criteria. Since the 2023 JCR release, journals in the Emerging Sources Citation Index also receive a JIF. After selection, a journal needs published items to be cited within the window before a meaningful figure exists.
Why does a small journal’s impact factor swing from year to year?
With few citable items, one highly cited paper can change the ratio a lot. Judge a small journal over several years, and look at the five-year JIF and category quartile as well.
Is a higher impact factor a sign of better research?
Not by itself. The San Francisco Declaration on Research Assessment (DORA) recommends against using journal-level metrics as a substitute for assessing individual papers. Use the JIF as one indicator among several.
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