Last Updated on July 1, 2026 by Dr. Bhagat
JOURNAL METRICS·Updated June 2026
How Impact Factor is calculated: complete guide to the JCR formula, two-year citation window, citable items definition, and worked examples. Covers the 2025 JCR methodology by Clarivate and common misconceptions about IF calculation.
The Impact Factor (IF) is a metric used to measure the relative importance of a journal within its field. It was developed by Eugene Garfield in the 1960s and remains one of the most widely used indicators of journal quality today. Understanding how Impact Factor is calculated helps researchers make informed decisions about where to submit their work.
GUIDE · Updated June 2026The Impact Factor Formula (With Example)
The Impact Factor is calculated by dividing the number of citations received by articles published in the journal over a two-year period by the total number of citable items published in those same two years.
| Component | Description |
|---|---|
| Numerator | Total citations in Year Y to articles published in Years Y-1 and Y-2 |
| Denominator | Total citable items (articles + reviews) published in Years Y-1 and Y-2 |
Formula:
IFY = Citations(Y-1 + Y-2) ÷ Articles(Y-1 + Y-2)
WORKED EXAMPLEStep-by-Step Calculation Example
Let’s calculate a fictional journal’s 2025 Impact Factor:
- A journal published 100 articles in 2023 and 120 articles in 2024.
- Those articles received 500 citations in 2025.
- The 2025 Impact Factor = 500 ÷ (100 + 120) = 2.27
Key Point: The Impact Factor is an average. Not every article in the journal gets 2.27 citations. Some get zero; others get hundreds. The IF measures the journal as a whole, not individual papers.
CALCULATION METHODSDifferent Methods Used to Calculate Impact Metrics
Several organizations calculate impact metrics using different methodologies:
| Method | Organization | Window | Database |
|---|---|---|---|
| Journal Impact Factor (JIF) | Clarivate (JCR) | 2 years | Web of Science |
| CiteScore | Elsevier (Scopus) | 4 years | Scopus |
| SJR (SCImago Journal Rank) | Scimago Lab | 3 years | Scopus |
| SNIP | CWTS Leiden | 3 years | Scopus |
JCR METHODJournal Citation Reports (JCR) Method
Clarivate’s Journal Citation Reports is the most widely used source for Impact Factor data. The JCR IF is calculated using the 2-year formula described above and is based exclusively on citation data from the Web of Science Core Collection.
The JCR release in June 2026 covers the 2025 data year, reporting citations received in 2025 to articles published in 2023–2024.
CITESCOREScopus CiteScore Method
Elsevier’s CiteScore uses a 4-year citation window rather than 2 years. This smooths out year-to-year volatility and gives a more stable metric. CiteScore also counts all document types (not just articles and reviews) in the denominator.
SJR & SNIPSJR and SNIP: Normalized Alternatives
SJR (SCImago Journal Rank): Accounts for the prestige of citing journals. A citation from Nature counts more than a citation from an unknown journal.
SNIP (Source Normalized Impact per Paper): Adjusts for differences in citation practices across fields. A SNIP of 1.0 means a journal performs at the global average for its subject area.
TAKEAWAYSKey Takeaways
Key Takeaways
- Impact Factor = Citations ÷ Articles over a 2-year window.
- JCR (Clarivate) and CiteScore (Scopus) use different methodologies and time windows.
- SJR weights citations by journal prestige; SNIP normalizes across subject fields.
- IF is an average — individual article performance varies widely.
- Always check which metric and year you’re comparing when evaluating journals.
FAQFrequently Asked Questions
What is the formula for calculating Impact Factor?
Impact Factor = Total citations in Year Y to articles published in Years Y-1 and Y-2, divided by the total number of citable items published in Years Y-1 and Y-2.
What is the difference between JCR and CiteScore?
JCR Impact Factor uses a 2-year window and is based on Web of Science data. CiteScore uses a 4-year window and is based on Scopus data. They are not directly comparable.
What is a good Impact Factor?
It depends on the field. In biology, 5+ is strong; in mathematics, 2+ is competitive. Always compare IF within the same subject category, not across disciplines.
Can Impact Factor be manipulated?
Yes — through practices like coercive citation, excessive self-citation, or publishing review articles (which tend to be cited more). Clarivate and Scopus both monitor and suppress suspicious patterns.
What is the 5-year Impact Factor?
The 5-year IF uses the same calculation but over a 5-year window instead of 2 years. It is more stable for fields where citations accumulate slowly.
Do all journals have an Impact Factor?
No. Only journals indexed in the Web of Science Core Collection (SCIE, SSCI, AHCI) receive a JCR Impact Factor. Scopus-indexed journals have CiteScore instead.
