Below are some research metrics that measure a journal's impact:
Journal Impact Factor (JIF): Is calculated by the average number of times articles from the journal published in the past two years have been cited in the JCR year.
CiteScore: Calculates the average number of citations given in a previous year to the publications that appeared in a journal in the three preceding years. It includes all types of documents in the calculation of the metric. CiteScore metrics are a family of eight complementary indicators: CiteScore, CiteScore Tracker, CiteScore Percentile, CiteScore Quartiles, CiteScore Rank, Citation Count, Document Count, and Percentage Cited.
SCImago Journal Rank (SJR): Is calculated from both the number of citations received by a journal as well as a measure of the importance or prestige of the journal. Subject field, quality, and reputation of the journal have a direct effect on this metric.
Source Normalized Impact per Paper (SNIP): Measures the average citation impact of the publications in a journal but then normalized or corrected for differences in citation practices between fields. SNIP is the ratio of a journal's average citation count per paper and the citation potential of its subject field.
Top Journal Percentile: Is based only on citations received by a journal and is defined by SJR and SNIP in Scopus. The values at the top 1%, 5%, 10% and 25% are calculated.
h5 index: Is a Google metric based on the articles published by a journal over the previous 5 calendar years. It is the largest number h such that h articles published in 2014-2018 have at least h citations each.
Journal Citation Reports offers a systematic means to evaluate the world's leading journals from different specialties with quantifiable information based on citation data. JCR provides several metrics: Journal Impact Factor, 5 Year Impact Factor, Immediacy Index, Quartiles & JIF Percentiles, Cited & Citing Half Life, etc. Journals may be browsed by "Title" or by "Category".
Example: Nature's metrics in JCR
Scopus provides a comprehensive and open metric for academic journals, conference proceedings, trade journals, and book series. Journals may be searched by Subject area, Title, Publisher or ISSN. Scopus also provides SJR and SNIP.
Example: Nature's metrics in Scopus
SCImago is a publicly available portal that includes the journals and country scientific indicators developed from the information contained in Scopus. SCImago provides several metrics: SJR, h-index, Total cites, Quartile ranking, etc. for academic journals in addition to book series, conferences and proceedings, and trade journals. Users can analyze journal rankings and country rankings. Journals may be searched by Subject Area and/or Subject Category, or by individual title.
Example: Nature's metrics in SCImago
Example: Nature's metrics in CWTS
Google Scholar provides h5-index and h5-median of the top 100 publications. It will only display the top 20 journals for each subject category. h5-median is based on h5-index, but instead h5-median for a publication is the median number of citations for the articles that make up its h5-index.
Example: Nature's metrics in Google Scholar