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Journal Quality

Measuring Journal Quality

Tools used in estimating journal quality include: 

Contact your Liaison Librarian for assistance in determining relevant resources for your discipline.

What are journal impact factors?

The impact factor is a measure of the frequency with which the "average article" in a journal has been cited in a particular year or period.

JCR® is the sole place where impact factors are calculated and reported. JCR® covers approximately 7,500 journal titles. This is a small minority of the journals in publication, so be aware: most journals do not have an impact factor.

Read about Thomson Scientific's journal selection process.

The Impact factor formula

ISI defines the impact factor as a ratio of two elements. The denominator is the total number of "citable" articles published in a particular journal within a given timeframe. The numerator is the total number of citations in the current year to any article published in this journal during that given timeframe. ISI has defined this time frame as two years.

The impact factor (IF) of journal A in a particular year Y is calculated using the following formula:

The impact factor formula

Be aware that...

  • Many journals do not have an impact factor.
  • The impact factor cannot assess the quality of individual articles. Even if citations were evenly distributed among articles, the impact factor would only measure the interests of other researchers in an article, not its importance and usefulness.
  • Only research articles, technical notes and reviews are “citable” items. Editorials, letters, news items and meeting abstracts are “non-citable items”.
  • Only a small percentage of articles are highly cited and they are found in a small subset of journals. This small proportion accounts for a large percentage of citations.
  • Controversial papers, such as those based on fraudulent data, may be highly cited, distorting the impact factor of a journal.
  • Citation bias may exist. For example, English language resources may be favoured. Authors may cite their own work.
  • Other tools available

See alternative tools on this page - SJR, ERA Journal List, JANE



Scopus is the world's largest abstract and citation database of peer-reviewed literature and quality web sources, with smart tools to track, analyze and visualize research. Find details about Scopus here.

How to Use Impact Factors

Impact factors can be used to:

  • identify journals in which to publish
  • identify journals relevant to your research
  • confirm the status of journals in which you have published

But what’s in a number? To state that the British Medical Journal (BMJ) has an impact factor of 9.052 is reasonably meaningless.

It is more meaningful to say that BMJ’s impact factor ranks sixth of 105 journals in the field of general and internal medicine. Or to compare the journal’s impact factor of 9.052 with the aggregate impact factor for its field: 4.326.

It is recommended therefore that the impact factor for a journal is not looked at in isolation. Rather, the impact factor of a journal should be compared to the impact factors for other journals within the same subject category.

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