The impact factor calculator above applies the published definition of the journal impact factor: citations received in one year to items published in the two preceding years, divided by the number of citable items published in those two years. It also computes the five-year variant, which uses a longer window, and shows what the two-year figure becomes if self-citations are excluded.
Arb Digital publishes it as an explanation of a metric, not as a scoreboard. The impact factor describes a journal, and it does so in a way that has been criticised in detail by the people who maintain it as well as by the research community. This page deliberately attaches no verdict to any value, presents no ranking, and does not treat a larger number as a better one. Our APA citation generator and MLA citation generator handle the referencing side of academic work.
What This Impact Factor Calculator Does
It performs one division and reports it four ways. The headline is the two-year impact factor. The five-year figure uses the same construction over a longer window and is included because it behaves differently in fields where research is cited slowly. The self-citation line shows the same two-year figure with journal self-citations removed from the numerator, which is the standard sensitivity check.
The ratio of the five-year to the two-year figure is the least familiar of the four and often the most informative. A ratio well above one means the journal's articles keep accumulating citations after the two-year window closes, which is normal in mathematics, ecology and much of the humanities. A ratio near or below one means citations arrive quickly and then stop, which is normal in fast-moving biomedical fields. Neither pattern is better; they are properties of the field.
Everything is an input. There is no embedded database of journals, no lookup and no published figures reproduced here, because the counts depend entirely on which citation index you use, which items that index classifies as citable, and which year's edition you are reading.
How to Use It
- Fix the reporting year first and note it. Every count must come from the same year and the same citation database.
- Enter citations received in that year to items published in the two preceding years — not total citations, and not citations to all past years.
- Enter the citable item counts for each of the two years separately. What counts as citable is a definition set by the index, not by you.
- Add the five-year figures if you have them, to see how much the window length changes the answer.
- Enter self-citations if you know the number, and compare the two figures. A large gap is worth understanding before quoting either.
The Formula and How It Is Calculated
The two-year impact factor for year Y is IF = A ÷ B, where A is the number of citations made during Y to items the journal published in Y−1 and Y−2, and B is the number of citable items the journal published in those same two years. The five-year version replaces the two-year window with a five-year one in both the numerator and the denominator.
Work the default through. In the reporting year the journal received 1,200 citations to items it published in the two previous years. It published 220 citable items one year before and 180 two years before, so B = 400. The impact factor is 1,200 ÷ 400 = 3.000.
For the five-year window, 4,200 citations against 1,050 citable items gives 4,200 ÷ 1,050 = 4.000. The ratio of the two is 4.000 ÷ 3.000 = 1.333, which says that citations to this journal continue to accumulate meaningfully after the two-year window closes. If 150 of the 1,200 citations were self-citations, the two-year figure without them would be 1,050 ÷ 400 = 2.625, a reduction of 12.5 percent. Clarivate, which publishes the metric, states on its Journal Citation Reports pages that the impact factor is a journal-level metric and is not a measure of a specific paper.
The Documented Criticisms
These are not fringe objections. They are set out by research organisations, by bibliometricians, and by the metric's own publisher, and anyone using the number should know them.
It describes a journal, not a paper. The impact factor is a mean over all citable items, and citation distributions within a journal are strongly right-skewed: a minority of articles attract a large share of the citations, and the median article in a journal typically receives far fewer citations than the impact factor. Inferring anything about a specific paper from the journal it appeared in is therefore an error of the same kind as inferring an individual's income from a national average.
It varies enormously by field. Citation practices differ in density and speed — how many references a typical paper carries, and how quickly work is cited after publication. A figure that is unremarkable in molecular biology would be exceptional in pure mathematics. Cross-field comparison of raw impact factors is not meaningful, and no normalisation built into the metric corrects for it.
It can be influenced by editorial policy. The denominator counts only items the index classifies as citable, while the numerator counts citations to everything the journal published, including editorials and letters. Shifting the mix of content changes the ratio without any change in the research. Review articles attract more citations than primary research, so publishing more of them raises the figure.
It should not be used to judge individuals. The San Francisco Declaration on Research Assessment asks funders, institutions and publishers not to use journal-based metrics as a proxy for the quality of individual research articles or for decisions about hiring, promotion or funding. Thousands of organisations have signed it. That recommendation is the single most important thing to know about this number, and it is the reason this page reports it without ranking anything.
Why the Denominator Is the Contested Part
Most disputes about a specific impact factor are disputes about B, not A. The numerator is a citation count and is comparatively mechanical. The denominator requires deciding which of a journal's published items are citable, and that is a judgement made by the index.
Research articles and reviews are counted. Editorials, letters, news items, corrections and commentary generally are not. But real journals publish material that sits on the boundary — a substantial commentary that reads like a review, a case report, a conference abstract — and how it is classified moves the denominator. Since the denominator is typically in the hundreds while the numerator is in the thousands, a reclassification of a few dozen items shifts the impact factor visibly.
This is also why an impact factor cannot be reliably recomputed from a journal's own website. The counts must come from the index that defines citable, using that index's coverage of the citing literature. A figure computed from different sources is a different statistic that happens to share a name. Our weighted average calculator is useful if you are combining figures across several journals and need the weights handled properly rather than averaging the averages.
What to Use Instead, and When
If the question is about a journal's overall citation profile, the impact factor is a legitimate if crude answer, and reading it alongside the five-year figure and the self-citation-adjusted figure gives a much better picture than the headline alone.
If the question is about a specific article, use that article's own citation count, and interpret it against the distribution for its field and its age rather than against the journal. If the question is about a researcher, DORA's position is that journal-level metrics should not be used at all, and that assessment should consider the content of the work and the full range of research outputs.
Because the underlying distribution is skewed, summary statistics that are robust to that skew are more informative than a mean. The median citation count for a journal's articles is routinely much lower than its impact factor, and the gap between them is itself a useful figure. Our median absolute deviation calculator gives a spread measure that is not dragged around by a handful of extreme values, and the percentage calculator handles the year-on-year comparisons.
Arb Digital builds free tools that compute the definition and state what the number cannot tell you.
Browse All Free Tools Talk To Our TeamCommon Mistakes to Avoid
- Using total citations in the numerator — only citations made during the reporting year, to items from the two preceding years, belong there.
- Counting all published items in the denominator — only items the index classifies as citable are counted, and editorials and letters generally are not.
- Comparing across fields — citation density and speed differ so much between disciplines that raw impact factors carry no cross-field meaning.
- Reading a journal figure as a statement about a paper — the distribution is skewed, so the typical article receives well below the mean.
- Quoting three decimal places as though they were precise — the underlying counts are subject to classification decisions that move the figure far more than the third decimal.
Related Free Tools From Arb Digital
Format references with the APA citation generator or the MLA citation generator, combine figures correctly with the weighted average calculator, measure spread without being dragged by outliers using the median absolute deviation calculator, or handle year-on-year change with the percentage calculator. The full free online tools hub lists every research and study tool we publish.
Frequently Asked Questions
It is the number of citations received in one year to items the journal published in the two preceding years, divided by the number of citable items it published in those two years.
Research articles and reviews, as classified by the citation index. Editorials, letters, news and corrections are generally excluded from the denominator even though citations to them count in the numerator.
It applies the same construction over a five-year window. It is more informative in fields where work is cited slowly, and the ratio between the two windows shows how quickly a journal's citations arrive.
No. It is a mean over a skewed distribution that describes a journal rather than any article in it, and it varies by field by more than it varies by quality. DORA asks assessors not to use it as a proxy for research quality.
Because disciplines differ in how many references a typical paper carries and how quickly work is cited. A figure that is ordinary in one field would be exceptional in another, and the metric contains no correction for this.
The San Francisco Declaration on Research Assessment is a statement asking funders, institutions and publishers not to use journal-based metrics as a surrogate for the quality of individual articles or researchers.
Citations from a journal to its own recent articles count in the numerator. Removing them is the standard sensitivity check, and a large gap between the two figures is worth understanding before quoting either.
Not reliably. The counts depend on one index's coverage of the citing literature and on its classification of citable items, so figures assembled from other sources are a different statistic with the same name.
This page explains how a bibliometric indicator is defined and computed, for educational purposes. It offers no assessment of any journal, article or researcher, and journal-level metrics should not be used to evaluate individual research.
