Two most widely used databases for journal metrics are Web of Science (Clarivate Analytics) and Scopus (Elsevier).
Main indicators in the Web of Science:
| Indicator | Definition |
| Journal Impact Factor, JIF | The Journal Impact Factor is defined as all citations to the journal in the current JCR year to items published in the previous two years, divided by the total number of scholarly items (these comprise articles, reviews, and proceedings papers) published in the journal in the previous two years. |
| Aggregate Impact Factor, AIF | The aggregate Impact Factor for a subject category is calculated the same way as the Impact Factor for a journal, but it takes into account the number of citations to all journals in the category and the number of articles from all journals in the category. An aggregate Impact Factor of 1.0 means that that, on average, the articles in the subject category published one or two years ago have been cited one time. |
| Total Cites | The total number of times that a journal has been cited by all journals included in the database in the Journal Citation Reports year. |
| Qartile in Category, Q | The Journal Impact Factor quartile is the quotient of a journal’s rank in category (X) and the total number of journals in the category (Y), so that (X / Y) = Percentile Rank Z. Q1: 0.0 < Z ≤ 0.25 Q2: 0.25 < Z ≤ 0.5 Q3: 0.5 < Z ≤ 0.75 Q4: 0.75 < Z |
| Eigenfactor Score | The Eigenfactor calculation is based on the number of times articles from the journal published in the past five years have been cited in the JCR year, but it also considers which journals have contributed these citations so that highly cited journals will influence the network more than lesser cited journals. References from one article in a journal to another article from the same journal are removed, so that Eigenfactors are not influenced by journal self-citation. |
| Article Influence Score | The Article Influence Score determines the average influence of a journal’s articles over the first five years after publication. It is calculated by multiplying the Eigenfactor Score by 0.01 and dividing by the number of articles in the journal, normalized as a fraction of all articles in all publications. |
| Self- citations | A self-citation is a reference to an article from the same journal. Self-citations can make up a significant portion of the citations a journal gives and receives each year. You can compare self-citing rates and self-cited rates to supplement your journal evaluation. |
| Immediacy Index | The Immediacy Index indicates how quickly articles in a journal are cited. It is calculated by dividing the number of citations to articles published in a given year by the number of articles published in that year. |
| Cited Half-Life | Median age of the articles that were cited in the JCR year. Half of a journal’s cited articles were published more recently than the cited half-life. |
Main indicators in Scopus (Elsevier):
| Indicator | Definition |
| CiteScore | CiteScore calculates the average number of citations received in a calendar year by all items published in that journal in the preceding three years. The calendar year to which a serial title’s issues are assigned is determined by their cover dates, and not the dates that the serial issues were made available online. |
| Source-Normalized Impact per Paper, SNIP | Source Normalized Impact per Paper (SNIP) accounts for field-specific differences in citation practices. It does so by comparing each journal’s citations per publication with the citation potential of its field, defined as the set of publications citing that journal. SNIP therefore measures contextual citation impact and enables direct comparison of journals in different subject fields, since the value of a single citation is greater for journals in fields where citations are less likely, and vice versa. |
| SCImago Journal Rank, SJR | SCImago Journal Rank (SJR) is based on the concept of a transfer of prestige between journals via their citation links. Drawing on a similar approach to the Google PageRank algorithm – which assumes that important websites are linked to from other important websites – SJR weights each incoming citation to a journal by the SJR of the citing journal, with a citation from a high-SJR source counting for more than a citation from a low-SJR source. |
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CiteScore Percentile |
CiteScore Percentile indicates the relative standing of a serial title in its subject field. Each subject field is divided into 100 equal-sized percentiles based on the number of serial titles, and a serial title is assigned to a percentile based on its CiteScore. |
| CiteScore Quartile | Quartiles are bands of serial titles that have been grouped together because they occupy a similar position within their subject categories. The quartiles are: Quartile 1: serial titles in 99-75th percentiles; Quartile 2: serial titles in 74-50th percentiles; Quartile 3: serial titles in 49-25th percentiles; Quartile 4: serial titles in 24-0th percentiles. A title might have a different quartile within each different subject area it is included in. |