The oldest and best known metric for measuring the impact of journals is the Journal Impact Factor (JIF or IF), determined by Clarivate's Journal Citation Reports. It is an average of the number of times articles published in a particular journal have been cited in the two previous years.
For example, if a journal has an impact factor of 15.84, this means that, on average, the articles published in this journal are cited approximately 16 times each in the two previous years:
Journal Citation Reports (JCR) is a well established source for journal rankings, including the Journal Impact Factor. JCR also partners with Eigenfactor.org, providing data for the calculation of additional metrics: the Eigenfactor and Article Influence. These are available via JCR or the separate link to Eigenfactor link below.
Scopus Journal Analyzer allows up to 10 journals to be compared according to assorted factors including SJR,and SNIP. These indicators can also be accessed freely through independent organizations linked below.