The Journal Impact Factor (JIF) is a metric from Clarivate Analytics that reflects the annual average number of citations to recent articles (previous two years) published in that journal. It is "a measure of the frequency with which the 'average article' in a journal has been cited in a particular year or period. The annual JCR impact factor is a ratio between citations and recent citable items published" (Clarivate Analytics).

Example:

A) In 2018, documents in Journal X in 2016 and 2017 were cited 300 times.
B) Journal X published 150 documents in 2016-2017.

The 2018 impact factor of Journal X = (A / B) = 300 / 150 = 2

Note: A = articles and reviews only. B = all citable documents.

Considerations:

• Based on Web of Science data (JIFs are only available for journals indexed in the Science Citation Index Expanded and the Social Sciences Citation Index)
• Not field normalized
• Uses a 2-year window
• There are many arguments for and against the JIF. See the Metrics Toolkit for a brief overview.

Find a Journal Impact Factor:

Journal Impact Factors are available from Journal Citation Reports (linked in the top menu of Web of Science).

The Eigenfactor Score is an indicator of a "journal's total importance to the scientific community" (Eigenfactor.org). It is calculated using an algorithm that considers the place of a citing journal within a network of citations.

The Normalized Eigenfactor Score rescales the Eigenfactor Score so that the average journal has a score of 1. This makes the scores easier to read and interpret: for example, a journal with a Normalized Eigenfactor Score of 3 has three times the total influence of the average journal.

Considerations:

• Based on Web of Science data
• Uses a 5-year window

Find an Eigenfactor Score:

Eigenfactor Scores are available in Journal Citation Reports and at http://www.eigenfactor.org.

A journal's Article Influence Score is "a measure of the average influence of each of its articles over the first five years after publication" (Eigenfactor.org). The average Article Influence Score of a journal in Journal Citation Reports is 1.00, so a journal with an article influence score of 25 has 25 times the influence of the average article in JCR.

SCImago Journal Rank (SJR) is a numeric indicator of journal prestige. It is calculated using Scopus data, and takes into account the average number of weighted citations received during a particular year per document published in that journal during the previous three years. Citations are weighted based on the closeness of the journals in a co-citation network (citations from closely related journals receive greater weight). For a detailed explanation, see About the SCImago Journal and Country Rank.

Considerations:

• Based on Scopus data
• Field normalized
• Uses a 3-year window
• Citable documents include articles, reviews, conference papers, and short surveys

Find a journal's SCImago Journal Ranking:

SCImago Journal Rankings are available at https://www.scimagojr.com.

CiteScore is a metric from Elsevier that measures the average number of citations received per document published in a particular journal.

Image source: https://blog.scopus.com/posts/citescore-2019-now-live

Considerations:

• Based on Scopus data
• Not field normalized
• Uses a 4-year window
• Considers peer-reviewed content (articles, reviews, conference papers, book chapters, and data chapters) for both numerator and denominator.

Find a journal's CiteScore:

CiteScores are available from the Sources menu in Scopus.

SNIP stands for Source Normalized Impact per Publication. This indicator was developed by CWTS (the Centre for Science and Technology Studies at Leiden University) and measures the average citation impact of papers in a particular journal.

Considerations:

• Based on Scopus data
• SNIP is field-normalized
• Uses a 3-year window
• Citable documents include articles, reviews, and conference papers
• CWTS provides a stability interval for the SNIP, which reflects the reliability of the indicator (the wider the stability interval, the less reliable the indicator)

Find a journal's SNIP:

SNIP indicators are available from CWTS Journal Indicators.