Calculate a journal impact factor from citations and citable items over a 2-year or 5-year window, or find the citations needed for a target.

Citations received in the JIF year to journal content from the selected previous years.

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Impact Factor Formulas

The standard two-year Journal Impact Factor is a citation-to-citable-item ratio reported by Journal Citation Reports. Select a solve mode, then enter a window total or each year’s counts and select Calculate. The estimator supports one to four displayed decimals; this does not add accuracy to the source data. Minimum-citation mode targets the exact entered unrounded ratio. Implied-item mode uses the ratio as exact and reports a fractional total plus a nearest positive whole-item estimate; a rounded published JIF does not determine a unique denominator.

IF = Cy / (Py - 1 + Py - 2)
  • Where IF is the 2-year Journal Impact Factor
  • Cy is the number of eligible citations received in the JCR year to the journal’s content published in Y-1 and Y-2, including citations to content types not counted in the denominator
  • Py-1 is the number of eligible citable items classified by Journal Citation Reports, primarily articles and reviews, published in Y-1
  • Py-2 is the number of citable items published two years prior (Y-2)

The 5-year JIF uses citations received in the JIF year to content from Y−1 through Y−5, divided by eligible citable items across those years. The numerator and denominator do not necessarily include the same document types. See Clarivate’s explanation of the numerator. CiteScore uses a different four-year method and data source.

Cumulative Impact Factor

The cumulative mode adds the journal impact factors associated with a list of papers. Enter one known JIF per paper, one per line, then select Calculate. If you have several papers in the same journal, enter its value once for each paper. The results show the sum, the number of included papers and their average JIF.

Cumulative JIF = JIF₁ + JIF₂ + … + JIFₙ
Average JIF = cumulative JIF ÷ n, where n is the number of included papers. For example, values of 1.1, 2.2 and 3.3 give a cumulative JIF of 6.6 across three papers and an average of 2.2.

Use a consistent rule for which JIF year to enter, such as the year required by your reporting policy. Leave unknown or unassigned JIFs out of the list and disclose that coverage; they are not measured zeros. This arithmetic summary is sometimes called a cumulative impact factor, but it is not an official author JIF, an h-index or a measure of an individual paper’s quality. Journal-level values should not substitute for assessment of the papers or researcher.

What Is a Journal Impact Factor?

A journal impact factor is a citation-based metric reflecting the average number of citations received per citable item published by a journal during a defined window. It was conceived by Eugene Garfield and Irving Sher in the early 1960s as a tool for librarians to evaluate journal subscriptions, not as a measure of individual article or researcher quality. Clarivate Analytics (formerly Thomson Reuters) publishes impact factors annually through the Journal Citation Reports, which as of 2024 covers over 21,900 journals across 254 subject categories.

The JIF denominator uses Clarivate’s citable-item classifications, primarily articles and reviews. The numerator includes eligible citations to journal content in the window, even when the cited content is not a denominator item. Use the actual JCR counts for the same metric year rather than an arbitrary database total.

Impact Factor Benchmarks by Field

Impact factors are not comparable across disciplines. A journal with an IF of 3.0 may rank in the top 10% of its category in mathematics but fall below the median in cell biology. This is because citation density, co-authorship norms, publication volume, and reference list lengths vary enormously by field.

There is no universal good-JIF threshold or fixed cross-field ranking. Compare the same metric year and relevant subject category using current JCR data; journal-level citation averages do not measure an individual article’s quality.

In fields like pure mathematics and many humanities disciplines, impact factors rarely exceed 3, and an IF of 1.5 can represent a top-tier journal. Engineering and computer science journals typically fall between 1 and 8. Biomedical and life sciences show the broadest range, with specialty clinical journals sometimes exceeding 50.

Journal Impact Factor vs. Other Citation Metrics

The impact factor is one of several journal-level metrics, each with distinct methodologies and data sources. Understanding their differences is essential for proper journal evaluation.

CiteScore counts citations received over four years to eligible documents published in the same four years, divided by those documents. Eligible types are articles, reviews, conference papers, book chapters and data papers, rather than every document type. See Elsevier’s current definition. The two metrics use different data and cannot be ranked by a universal conversion.

SJR (SCImago Journal Rank) operates similarly to Google's PageRank algorithm. It assigns different weights to citations based on the prestige of the citing journal. A citation from Nature carries more weight than one from a low-ranked journal. SJR also normalizes for field differences, making it more suitable for cross-discipline comparison than raw JIF. It uses a 3-year citation window and is freely available through the SCImago portal.

SNIP (Source Normalized Impact per Paper) explicitly corrects for citation potential. In fields where articles tend to include long reference lists (like biomedicine), each individual citation is worth less in the SNIP calculation. In fields with shorter reference lists (like mathematics), each citation counts for more. This makes SNIP the most directly cross-field-comparable metric among the four.

Journal Citation Indicator (JCI) was introduced by Clarivate in 2021 as a field-normalized metric. It normalizes each article's citation count against the average for its subject category and publication year, then averages across the journal. A JCI of 1.0 means the journal performs at the field average; above 1.0 means above average.

Limitations and Criticisms

The impact factor has faced sustained criticism from researchers, funders, and institutions since at least the early 2000s. The core objections center on statistical validity, field bias, and susceptibility to manipulation.

Citation distributions within journals are highly skewed. In a typical journal, roughly 15% to 20% of articles account for about 50% of all citations. The mean (impact factor) therefore misrepresents the citation count of any individual paper. A journal with an IF of 5 may contain articles cited 200 times alongside articles cited zero times.

The 2-year window is too short for fields where citations accumulate slowly. In mathematics, many foundational papers receive the bulk of their citations 5 to 10 years after publication, making the 2-year JIF a poor reflection of their influence. The 5-year IF partially addresses this but remains uncommon in evaluations.

Self-citation manipulation has been documented extensively. Some journals have had their impact factors suppressed by Clarivate after investigations revealed that over 90% of the citations contributing to their IF came from their own publications. Common gaming tactics include coercive citation (requiring authors to add references to the journal during peer review), strategic publication of review articles (which receive more citations than original research), and editorial timing to shift publications between JCR years.

DORA and the Reform Movement

The San Francisco Declaration on Research Assessment (DORA), established in 2012 at the annual meeting of the American Society for Cell Biology, directly recommends against using journal impact factors as proxy measures for individual article quality or for making hiring, promotion, or funding decisions. As of 2024, more than 22,300 individuals and organizations across 159 countries have signed DORA, including major funders like the Wellcome Trust, the European Research Council, and the Canadian Institutes of Health Research.

Several universities have formally restructured their tenure criteria in response. Ghent University (Belgium) adopted new evaluation standards in 2020 prioritizing open science practices over journal-level metrics. The University of Glasgow and the University of Zurich followed in 2021. Despite these institutional shifts, research indicates that journal rank still correlates strongly with perceived quality in practice, and no single alternative metric has replaced the impact factor in day-to-day academic decision-making.

Where to Find Official Impact Factors

The Journal Citation Reports (JCR) from Clarivate Analytics is the only official source for Journal Impact Factors. Access requires a subscription, typically provided through university libraries. JCR releases updated impact factors once per year, usually in late June. For CiteScore, SJR, and SNIP, the Scopus Sources tool (free to query) provides current and historical values. The SCImago Journal and Country Rank portal offers free SJR lookups. Google Scholar Metrics provides h5-index values for journals but does not calculate impact factors.

FAQ

What is a good impact factor for a journal? No single cutoff applies to every field. Compare journals within the same JCR category and year, and assess article quality separately from journal citation metrics.

What are the highest impact factor journals? Rankings change with each JCR release and depend on the metric year and eligible journal set. Consult the current JCR ranking rather than treating historical values as current.

Why does the impact factor matter? The impact factor serves as one indicator of how frequently a journal's recent articles are cited on average. It is used by librarians for subscription decisions, by publishers for marketing, and by researchers for choosing where to submit. However, DORA and many research institutions now recommend using it alongside article-level metrics, peer review assessments, and broader impact indicators rather than as a standalone quality measure.

What is the difference between impact factor and CiteScore? JIF uses citations in a single metric year to prior content, with a two-year or five-year publication window and Clarivate’s denominator classifications. CiteScore uses citations and eligible documents from the same four-year interval in Scopus; it includes five peer-reviewed document types. Neither is universally higher.

How long before a new journal gets an impact factor? Eligibility and first-release timing depend on Clarivate’s current selection policies, coverage and available publication history. Do not assume that every new journal receives a JIF on a fixed three-year schedule.

Can impact factors be manipulated? Yes. Documented manipulation tactics include coercive citation (journals requiring authors to cite their own recent papers), excessive self-citation orchestrated through editorial policy, strategic timing of article publication to shift items between JCR calculation years, and disproportionate publication of review articles that attract more citations. Clarivate monitors for anomalous self-citation patterns and has suppressed impact factors for journals caught engaging in these practices.