The impact factor (IF) is a measure of the frequency with which articles published in a scientific journal are cited in other academic papers. It is the most widely used metric for evaluating the relative importance or prestige of a journal within its field. The impact factor is published annually by Clarivate Analytics in the Journal Citation Reports (JCR).What Is Impact Factor?
The standard two-year impact factor is calculated as:
IF = (Citations in Year X to articles published in Years X-1 and X-2) ÷ (Total citable articles published in Years X-1 and X-2)
For example, if a journal published 200 articles in 2023–2024 and those articles received 600 citations in 2025, the 2025 impact factor would be 3.0.
Journal Impact Score vs. Impact Factor: What's the Difference?
The terms journal impact score and impact factor are often used interchangeably, but they refer to slightly different things:
- Impact Factor (IF) — Published by Clarivate. Uses a 2-year citation window. Only available for journals indexed in Web of Science.
- Impact Score (IS) — A Scopus/ScimagoJR metric. Uses a 2-year citation window similar to IF but draws from Scopus data. Available for a broader set of journals.
- CiteScore — Published by Elsevier/Scopus. Uses a 4-year citation window, generally producing higher numbers than IF.
- SJR (SCImago Journal Rank) — Weights citations by the prestige of the citing journal.
- SNIP (Source Normalized Impact per Paper) — Adjusts for citation density differences between fields.
When a researcher says "impact factor," they almost always mean the Clarivate JCR impact factor.
What Is a Good Impact Factor?
Whether an impact factor is "good" is entirely relative to the research field. Citation norms vary enormously between disciplines. A journal with an IF of 2.0 might be highly prestigious in mathematics but considered low in molecular biology.
| Impact Factor Range | General Interpretation |
|---|---|
| < 1.0 | Low — typical for niche, humanities, or new journals |
| 1.0 – 2.0 | Average — solid journal in most fields |
| 2.0 – 5.0 | Good — respected journal, recommended for career progression |
| 5.0 – 10.0 | Very Good — top-tier in most fields |
| 10.0 – 20.0 | Excellent — among the best journals in the field |
| > 20.0 | Elite — top multi-disciplinary or highly cited specialty journals |
Good Impact Factor by Field
- Medicine/Clinical Research: An IF of 5+ is good; IF 10+ is excellent
- Biology/Biochemistry: IF 3+ is solid; IF 8+ is excellent
- Physics: IF 2+ is good; IF 5+ is excellent
- Mathematics: IF 1.5+ is strong; IF 3+ is exceptional
- Engineering: IF 2+ is good; IF 6+ is excellent
- Social Sciences: IF 1+ is solid; IF 3+ is excellent
- Humanities: Many journals are not IF-ranked; peer reputation matters more
Many funding agencies and universities use impact factor quartiles (Q1, Q2, Q3, Q4) relative to the journal's field category. A Q1 or Q2 journal is generally considered a strong publication target, regardless of the absolute IF number.
Highest Impact Factor Journals in the World (2025)
The journals with the highest impact factors are predominantly multi-disciplinary mega-journals or top specialty publications in high-citation fields like medicine and cell biology.
| Journal | Field | Impact Factor (approx.) |
|---|---|---|
| CA: A Cancer Journal for Clinicians | Oncology | ~503 |
| Nature Reviews Drug Discovery | Pharmacology | ~120 |
| Nature Reviews Molecular Cell Biology | Cell Biology | ~113 |
| New England Journal of Medicine (NEJM) | Medicine | ~96 |
| Nature | Multidisciplinary | ~50 |
| Science | Multidisciplinary | ~44 |
| The Lancet | Medicine | ~99 |
| Cell | Cell Biology | ~45 |
| JAMA | Medicine | ~120 |
| Nature Medicine | Medicine | ~58 |
Note: These values change annually. Always check the latest JCR release (typically published in June each year) for current figures. You can browse journals by impact factor on JournalsHub.
Publication Impact Factor: Why It Matters for Your Career
Where you publish significantly affects your academic reputation, grant funding prospects, and career advancement opportunities. Here's why the publication impact factor matters:
1. Tenure and Promotion
Many universities use impact factor as a proxy metric when evaluating faculty for tenure or promotion. Publishing consistently in high-IF journals strengthens your case significantly.
2. Grant Funding
Funding agencies such as NIH, Wellcome Trust, and national science foundations often look at where researchers have previously published when assessing grant applications.
3. h-Index and Citation Count
Publishing in high-IF journals increases the probability that your work will be cited, which improves your personal h-index — a measure of both productivity and citation impact.
4. Visibility and Readership
High-impact journals have larger readerships, editorial boards, and indexing coverage, meaning your research reaches more scientists worldwide.
Limitations of Impact Factor
Despite its widespread use, the impact factor has significant criticisms:
- Skewed by a few highly cited papers — The IF is a mean, not a median. A handful of extremely cited papers can inflate a journal's IF while most papers receive few citations.
- Field dependency — Cross-field comparisons are meaningless. An IF of 3 in mathematics and an IF of 3 in biochemistry do not represent equivalent journal quality.
- Review articles inflate IF — Review articles receive many more citations than original research, so journals that publish many reviews tend to have higher IFs.
- Open to gaming — Journals can encourage self-citation or submit manipulated citation data (leading to some being delisted from JCR).
- Not applicable to all fields — Arts, humanities, and some social science journals may not be indexed in JCR at all.
The San Francisco Declaration on Research Assessment (DORA) and the Leiden Manifesto urge the academic community to reduce over-reliance on impact factor in research evaluation.
Alternatives to Impact Factor
- CiteScore — Broader, uses 4-year window, free to access via Scopus
- SJR — Accounts for citing journal quality (like Google PageRank for journals)
- SNIP — Field-normalized, removes citation density bias
- h5-index — Google Scholar's metric: the h-index for articles published in the last 5 years
- Altmetrics — Measures online attention: social media mentions, news coverage, policy documents
How to Find a Journal's Impact Factor
Here are the best ways to look up a journal's current impact factor:
- JournalsHub — Search our journal database for IF, CiteScore, SJR, APC, and acceptance rates all in one place
- Clarivate JCR — Official source for IF; requires institutional subscription
- Scopus — For CiteScore and SJR metrics; available via institutional access
- SCImago Journal Rank — Free at scimagojr.com
- Journal homepage — Most journals display their latest IF on their official website
Frequently Asked Questions
Is a higher impact factor always better?
Not necessarily. The best journal for your paper is one whose audience is most relevant to your research. A highly specialized journal with a moderate IF may give your work better visibility and citation potential within its target community than a broad journal with a high IF where it may be overlooked.
Can a journal lose its impact factor?
Yes. Clarivate can suppress or delist a journal from JCR if it violates citation ethics (e.g., excessive self-citation or citation stacking). Once delisted, the journal loses its official impact factor.
When are new impact factors released?
Clarivate typically releases the new Journal Citation Reports (and thus the updated impact factors) each June for the preceding calendar year.
Does impact factor apply to books or conference papers?
No. Impact factor applies only to journals indexed in Web of Science. Books, book chapters, and most conference proceedings do not have impact factors, though they may have alternative citation metrics.
Conclusion
The impact factor remains the dominant metric for journal prestige in academia, despite its limitations. Understanding what it measures, how to interpret it relative to your field, and how to use it alongside complementary metrics like CiteScore and SJR will help you make smarter publishing decisions. Use JournalsHub's journal search to find and compare journals by impact factor, APC, acceptance rate, and more.