The Two Main Journal Metrics
When evaluating academic journals, you will encounter two primary metrics: Impact Factor (IF) published by Clarivate, and CiteScore published by Elsevier/Scopus. Both measure how often a journal's articles are cited, but they differ significantly in methodology, coverage, and typical values.
Impact Factor: How It Works
The Journal Impact Factor (JIF) is calculated annually by Clarivate and published in the Journal Citation Reports (JCR). The formula uses a 2-year citation window:
IF = Citations in Year X to articles published in X-1 and X-2 ÷ Citable articles published in X-1 and X-2
Key properties:
- Only covers journals indexed in Web of Science (approx. 21,000 journals)
- Uses a 2-year window — advantages journals with fast-turnaround citation cultures (biomedicine) over slower fields (mathematics, humanities)
- Counts only "citable items" (articles and reviews) in the denominator but all citations in the numerator, which can inflate the metric
- Requires an institutional subscription to JCR to access official values
CiteScore: How It Works
CiteScore is calculated by Elsevier using Scopus data. It uses a 4-year citation window:
CiteScore = Citations in Year X to documents published in X-1, X-2, X-3 and X-4 ÷ All documents published in X-1, X-2, X-3 and X-4
Key properties:
- Covers journals indexed in Scopus (approx. 25,000+ journals) — broader than JCR
- Uses a 4-year window — steadier and less skewed by a single exceptional year
- Counts all document types in both numerator and denominator (including letters, editorials, conference papers) — generally gives lower values than IF for the same journal
- Free to access via Scopus (no subscription needed for the metric itself)
Direct Comparison
| Feature | Impact Factor | CiteScore |
|---|---|---|
| Published by | Clarivate (JCR) | Elsevier (Scopus) |
| Citation window | 2 years | 4 years |
| Journal coverage | ~21,000 | ~25,000+ |
| Denominator | Citable items only | All documents |
| Free access | ❌ Subscription required | ✅ Free |
| Self-citation protection | Limited | Better |
| Typical value | Higher (narrower denominator) | Lower (broader denominator) |
Other Important Metrics
SJR (SCImago Journal Rank)
SJR is like Google PageRank for journals — a citation from a high-prestige journal counts more than one from a low-prestige journal. Published free by SCImago, it can be a better indicator of journal influence rather than raw citation volume. Displayed at scimagojr.com.
SNIP (Source Normalised Impact per Paper)
SNIP adjusts for differences in citation behaviour between fields. A SNIP of 1.00 means the journal's citation impact matches the average across all Scopus journals in its field. SNIP is arguably the fairest metric for cross-disciplinary journal comparisons.
Eigenfactor Score
The Eigenfactor Score (available free at eigenfactor.org) estimates the influence of a journal based on the entire network of citations, not just recent ones. It removes self-citations and weights citations by the prestige of the citing journal, similar to SJR but using WoS data.
h5-index (Google Scholar)
The h5-index is the h-index for articles published in the last 5 years. It is calculated by Google Scholar Metrics and is free. It is a good measure of a journal's recent impact, particularly useful for newer journals that may not yet have a JCR Impact Factor.
Which Metric Should You Use?
| Situation | Best Metric |
|---|---|
| Comparing journals for promotion dossier (most institutions) | Impact Factor (JCR) |
| Checking a journal not in JCR | CiteScore or SJR |
| Comparing journals across different fields | SNIP |
| Evaluating journal prestige/influence (not just volume) | SJR |
| Checking a journal's recent performance | h5-index or CiteScore |
| Free, quick check | CiteScore or SJR |
Frequently Asked Questions
Why is a journal's CiteScore much lower than its Impact Factor?
Primarily because CiteScore uses a 4-year window and counts all document types in the denominator (including editorials and letters that attract few citations). For most journals, CiteScore ≈ 0.75–0.85× the Impact Factor, though this varies.
Can a journal have CiteScore but no Impact Factor?
Yes. Many Scopus-indexed journals that are not in Web of Science have a CiteScore but no official JCR Impact Factor. This is common for newer journals or regional publications.
Conclusion
Both metrics are useful and measure slightly different things. For formal academic evaluation, the Impact Factor remains the standard in most institutions. For comprehensive journal research — especially for journals outside JCR — use CiteScore, SJR, and SNIP in combination. JournalsHub displays IF, CiteScore, and SJR side-by-side, so you can compare journals across all metrics at once.