The metrics provide alternative, transparent and accurate views of the citation impact a journal makes, and are all available for free download.. The impact metrics are based on methodologies developed by external bibliometricians and use Scopus as the data source.
Source Normalized Impact per Paper (SNIP)
SNIP measures contextual citation impact by weighting citations based on the total number of citations in a subject field. The impact of a single citation is given higher value in subject areas where citations are less likely, and vice versa. As a field-normalized metric SNIP offers researchers, authors and librarians the ability to benchmark and compare journals from different subject areas. A component of the SNIP calculation is the raw Impact per Publication (IPP) which measures the ratio of citations per article published in the journal.
SCImago Journal Rank (SJR)
SJR is a prestige metric based on the idea that ‘all citations are not created equal’. With SJR, the subject field, quality and reputation of the journal have a direct effect on the value of a citation. It is a size-independent indicator and it ranks journals by their ‘average prestige per article’ and can be used for journal comparisons in the scientific evaluation process.