Journal Impact Factors (JIF) are created from an analysis of the citation data in the Web of Science database. Theoretically, the higher the impact factor, the more prestigious the journal. Impact Factors are updated once a year in the Journal Citation Reports (JCR) database.
The Impact Factor is calculated by dividing the number of citations to the journal 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 years ago have been cited one time in the current JCR year. For example, a journal with a JIF of 1.0 in the 2015 JCR would have articles published in 2013 & 2014 that have been cited once in 2015. An Impact Factor of 2.5 means that, on average, the articles published in 2013 & 2014 were cited 2.5 times in 2015. Citing articles may be from the same journal, or from different journals.
There are some caveats that must be noted:
Go to the Journal Citation Reports database:
For a Single Title search, click the 'Select Journals' option in the left column and simply type in the full name of the journal. You can select more than one title at a time. Then browse to the bottom of the page again and click 'submit'.
For a Subject search, click the 'select categories' option in the left column and click the check box next to the appropriate category. You can select more than one category at a time. Then browse down to the bottom and click 'submit'.
The journal impact factor is the orange column.
For a Subject Category search, the default sort is by impact factor. You can change the sort (by clicking the column heading) to:
You can customize the indicators shown by clicking on the 'Customize Indicators' option in the top left. Other indicators often usefule include:
Eigenfactor and Article Influence scores are also available directly, for free, at Eigenfactor.org.
The Eigenfactor uses Thomson Reuters (ISI Web of Knowledge) citation data to compute EI and AI scores.
A journal's Eigenfactor (EF) Score is a measure of the journal's importance to the scientific community. Eigenfactor scores are scaled so that the sum of the Eigenfactor scores of all journals listed in Thomson's Journal Citation Reports (JCR) is 100. In 2009, the journal Nature has the highest Eigenfactor score, with a score of 1.74605. The top thousand journals, as ranked by Eigenfactor score, all have Eigenfactor scores above 0.01.
Like the Impact Factor, the Eigenfactor Score is essentially a ratio of number of citations to total number of articles. However, unlike the Impact Factor, the Eigenfactor Score:
Article Influence scores
A journal's Article Influence (AI) score measures the average influence, per article, of the papers in a journal. As such, it is comparable to Thomson Scientific's widely-used Impact Factor. Article Influence scores are normalized so that the mean article in the entire Thomson Journal Citation Reports (JCR) database has an article influence of 1.00.
There are many other journal measures. An explanation of them is available here:
Walters, W. H. (2016). Information sources and indicators for the assessment of journal reputation and impact. The Reference Librarian, 57(1), 13-22. doi:10.1080/02763877.2015.1088426
Various journal measures can be found at the following sites:
CiteScore: is the average number of citations received by a journal in a calendar year divided by all items published in that journal in the preceding three years.
Teixeira da Silva, Jaime A, & Memon, A. R. (2017). CiteScore: A cite for sore eyes, or a valuable, transparent metric? Scientometrics, 111(1), 553-556.
SNIP: Source Normalized Impact per Paper is defined as the ratio of a journal’s citation count per paper and the citation potential in its subject field.2 It compares directly to Web of Knowledge’s Impact Factor. SJR is based on times cited, but also uses an algorithm similar to Google’s PageRank to calculate article influence, which it uses to create rankings; it accounts for both the number of citations received by a journal and the prestige of the journals where such citations originated. Users can compare rankings of up to ten journals at a time and display top journals.
H Moed. "Measuring contextual citation impact of scientific journals." Journal of Informetrics 4 (3): 265-277; July 2010. doi: 10.1016/j.joi.2010.01.002
SJR: SCImago Journal Rank indicates the influence of the average article from the journal. It is a measure of scientific influence of scholarly journals that accounts for both the number of citations received by a journal and the importance or prestige of the journals where such citations come from.1 With SJR, the subject field, quality and reputation of the journal have a direct effect on the value of a citation.
Borja González-Pereira, Vicente P. Guerrero-Bote, Félix Moya-Anegón. "A new approach to the metric of journals’ scientific prestige: The SJR indicator" Journal of Informetrics 4 (3): 379-391; July 2010. doi: 10.1016/j.joi.2010.03.002.
IPP: Impact Per Publication is the number of citations given in the present year to publications in the past three years divided by the total number of publications in the past three years