Citation metrics

There is an increasing number of measurements of the impact of journals and their articles on the research community. Most of these are based, in some way, on the level of citations but there are many different models now in use. We list below some of the more established ones and we plan to extend this list as and when newer metrics become available in order to give the fullest possible picture of our journals' performance.

  1. Impact Factor and related measures

  2. Eigenfactor

  3. Journal-level metrics

  4. Article usage statistics

  5. Altmetric scores

The Impact Factor and related measures

Impact factor: a measure of how often an average article in a journal has been cited. The impact factor of a journal is calculated by dividing the number of current year citations to source items published in that journal during the previous two years. Whilst it is a relatively easy measure to calculate and understand, it does have certain limitations. Given the highly skewed nature of the citation distribution of a journal's articles, the appropriateness of using a mean has been questioned. Also, most journals contain a significant proportion of articles that are never cited. Such articles can be seen as "benefitting" unfairly from the impact factor of the journal they appear in.

The impact factor is a "per article" metric and therefore normalises out the size of the journal.

5 year Impact Factor: is the impact factor calculated using a base of five years worth of cited articles, rather than two. This gives a fairer picture of journals in fields with slower citation patterns, such as mathematics.

Cited half-life: the number of years, counting back from the current year, which account for half the total citations received by the cited journal in the current year. This provides an measure of how "long-lived" the articles are in terms of their influence on the literature.

Immediacy index: the average number of times that an article is cited in the same year it is published. It gives an indication of how topical the material in the journal is.

Further information on the Impact Factor


2013 Impact Factor


5 year Impact Factor

Cited half-life

Immediacy Index

Proceedings A


11th out of 55 in "Multidisciplinary Sciences"




Proceedings B


9th out of 83 in "Biology"




Philosophical Transactions A


9th out of 55 in "Multidisciplinary Sciences"




Philosophical Transactions B


6th out of 83 in "Biology"






7th out of 55 in "Multidisciplinary Sciences"




Biology Letters


15th out of 83 in "Biology"




Interface Focus


 17th out of 83 in "Biology"




Open Biology


 67th out of 290 in "Biochemistry and Molecular Biology" 




Impact Factors of Royal Society journals since 1994














Eigenfactor and related measures

The Eigengactor differs from the Impact Factor in a number of important ways. It is not a "per article" metric, but instead gives an indication of the overall contribution of the journal - as a whole - to the literature. It does this using an algorithm similar to that of Google's "page rank" to count citations into and out of the journal and to weight them according to the ranking of the source or destination. It uses the Thomson Scientific journal dataset. It is intended to measure how likely a journal is to be used or the amount of time a reader will spend reading it. Large journals rank more highly in the Eigenfactor system than do small journals (in contrast to the Impact Factor, which is independent of size).

Further information on the Eigenfactor

Article Influence: measures the relative importance of the journal on a per-article basis. It is the journal's Eigenfactor Score divided by the fraction of articles published by the journal. That fraction is normalized so that the sum total of articles from all journals is 1.

The mean Article Influence Score is 1.00. A score greater than 1.00 indicates that each article in the journal has above-average influence. A score less than 1.00 indicates that each article in the journal has below-average influence.


2013 Eigenfactor

Eigenfactor Rank

Article Influence

Article Influence Rank

Proceedings A


10th out of 56 in "Multidisciplinary Sciences"


10th out of 56 in "Multidisciplinary Sciences"

Proceedings B


2nd out of 83 in "Biology"


10th out of 83 in "Biology"

Philosophical Transactions A


8th out of 56 in "Multidisciplinary Sciences"


7th out of 56 in "Multidisciplinary Sciences"

Philosophical Transactions B


3rd out of 83 in "Biology"


4th out of 83 in "Biology"



9th out of 55 in "Multidisciplinary Sciences"


6th out of 55 in "Multidisciplinary Sciences"

Biology Letters


7th out of 83 in "Biology"


14th out of 83 in "Biology"

Interface Focus


 37th out of 83 in "Biology"


 19th out of 83 in "Biology"

Open Biology


 220th out of 291 in "Biochemistry and Molecular Biology"


33rd out of 291 in "Biochemistry and Molecular Biology"


Journal level metrics

Every month, our journals collect and update two lists of popular articles as given below. The links are to examples in Open Biology.

Most-Read Articles: based on full-text and pdf views and updated monthly
Most-Cited Articles: based on citations to articles from HighWire-hosted articles and recalculated monthly


Article usage statistics

All Royal Society journals publish article usage statistics (information on downloads) alongside each individual article. Information on how to access individual article usage statistics via our website is shown below:

Article Usage StatisticsArticle Usage Statistics - detail


























Altmetric scores

Open Biology and Royal Society Open Science use the Altmetric doughnut to track the online activity around an article. Altmetric maintain a cluster of servers that watch social media sites, newspapers and magazines for any mentions of scholarly articles; the aim is to help authors to quantify the attention their article is receiving and readers establish those papers that their peers think are interesting. You can find more information about how the data is collected at

The Altmeric doughnut can be found on the "Info & Metrics" tab of each article. Except where there is no recorded data, each article is given an infographic and a score as shown below.

Altmetric in use