The journal impact factor, introduced by Eugene Garfield and published each year by Clarivate in the Journal Citation Reports, measures how often the average recent article in a journal is cited. For the year 2025, it counts all citations made during 2025 to anything the journal published in 2023 and 2024, and divides by the number of “citable items” – research articles and reviews – it published in those two years.
A value of 2.0 means an average recent article was cited twice in one year. Because citation habits differ hugely between fields, impact factors are only comparable within a discipline: top mathematics journals sit around 3–5, while leading medical journals exceed 50. The five-year impact factor uses five publication years in the denominator and suits fields where citations accumulate slowly.
Remember that the numerator counts citations to all content, including editorials and letters, while the denominator counts only citable items – one reason the metric can be gamed. The San Francisco Declaration on Research Assessment (DORA) advises against using it to judge individual papers or researchers.
How to use the Impact Factor Calculator
- Impact factor type
- Citations received in the census year
- Citable items published in the previous year (y−1)
- Citable items published in y−2
- Citable items published in y−3
- Citable items published in y−4
- Citable items published in y−5
Results update as you type, every field has its own unit menu, and everything is calculated in your browser.
How it works
Add the citable items published in the counted years, divide the citations received in the census year to those years’ content by that total, and report the ratio.
Worked example
A journal published 36 citable items in 2024 and 38 in 2023, and in 2025 those years’ content was cited 98 times. 2025 impact factor = 98 ÷ (36 + 38) = 98 ÷ 74 = 1.324. To raise it to 2.324 the journal would need 74 more citations.
Inputs explained
| Field | What to enter |
|---|---|
| Impact factor type | Choose one: Two-year impact factor, Five-year impact factor |
| Citations received in the census year | A number |
| Citable items published in the previous year (y−1) | A number |
| Citable items published in y−2 | A number |
| Citable items published in y−3 | A number |
| Citable items published in y−4 | A number |
| Citable items published in y−5 | A number |
Example values
How the main result changes when Citations received in the census year changes and everything else stays at the example values above:
| Citations received in the census year | Impact factor |
|---|---|
| 49 | 0.662 |
| 73.5 | 0.993 |
| 98 | 1.324 |
| 122.5 | 1.655 |
| 147 | 1.986 |
| 196 | 2.649 |
Formula
JIF(y) = citations in year y to items from y−1 and y−2 ÷ citable items published in y−1 and y−2 · 5-year JIF uses y−1 … y−5
Worked example
Inputs — Impact factor type: Two-year impact factor; Citations received in the census year: 98; Citable items published in the previous year (y−1): 36; Citable items published in y−2: 38.
Results — Citable items counted = 74; Impact factor = 1.324; Citations needed for an impact factor 1.0 higher = 74.
Key terms
- Census year
- The year in which citations are counted.
- Citable items
- Research articles and reviews (not editorials or letters).
- Journal Citation Reports
- Clarivate's annual database of journal metrics.
Frequently asked questions
How is the impact factor calculated?
Citations in year y to items published in the two previous years ÷ citable items published in those two years: 98 ÷ (36 + 38) = 1.324.
What is a good impact factor?
It depends on the field. Above 1 is respectable in many disciplines, above 10 is exceptional outside biomedicine.
Who publishes official impact factors?
Clarivate, in the Journal Citation Reports, every June for the previous year.
When does a new journal get an impact factor?
After it has been indexed for at least two full publication years plus the census year.
What is the five-year impact factor?
The same ratio using five years of publications – useful in slowly citing fields.
Can I compute an impact factor for a researcher?
Not meaningfully; the h-index or field-normalised metrics are used for individuals.