Guides @ UF: Research Metrics: Measuring the Influence and Impact of Research: Journal Impact & Ranking

What is the Impact Factor?

The journal Impact Factor is the average number of times articles from the journal published in the past two years have been cited in the JCR year.

The Impact Factor is calculated by dividing the number of citations in the JCR year by the total number of articles published in the two previous years. An Impact Factor of 1.0 means that, on average, the articles published one or two year ago have been cited one time. An Impact Factor of 2.5 means that, on average, the articles published one or two year ago have been cited two and a half times. Citing articles may be from the same journal; most citing articles are from different journals.

For example, the journal PLoS Biology's 2022 impact factor is 9.8.

This was calculated thusly:

6,192 - total of all citations from 2022 articles to PLoS Biology articles published in 2020 (3,839) and 2021 (2,353)

divided by

634 - total of PLoS Biology articles published in 2020 (347) and 2021 (287)

= 9.8

The number by itself does not mean as much. If you knew that the journal with the highest impact factor has the number 254.7, you might think 9.8 was quite low. But when you look at the impact factors of all the Biology journals indexed by JCR, PLoS Biology is ranked No. 4 in the Biology subject category.

Journal Citation Reports (JCR)

Journal Impact Factors can be found in the Thomson Reuters' resource, Journal Citation Reports (JCR).

More JCR Metrics

In addition to the Impact Factor, JCR will also include the following metrics for a journal

Article Influence Score
The Article Influence determines the average influence of a journal's articles over the first five years after publication. It is calculated by dividing a journal’s Eigenfactor Score by the number of articles in the journal, normalized as a fraction of all articles in all publications.
Eigenfactor Score
The Eigenfactor Score calculation is based on the number of times articles from the journal published in the past five years have been cited in the JCR year, but it also considers which journals have contributed these citations so that highly cited journals will influence the network more than lesser cited journals. References from one article in a journal to another article from the same journal are removed, so that Eigenfactor Scores are not influenced by journal self-citation.
Five-Year Impact Factor
The Impact Factor using 5 instead of 2 years
Immediacy Index
The Immediacy Index is the average number of times an article is cited in the year it is published.

SCImago

SCImago Journal and Country Rank is a portal that includes the journals and country scientific indicators developed from the information contained in the Scopus® database.