Impact factor for a journal
Impact factor is a measurement of a journal's impact. However, it tells nothing about how much an individual article will be quoted. Even in journals with a high impact factor, a clear majority of articles receive few or no citations at all.
The Web of Science contains some 21,000 scientific journals, of which about 12,000 have an impact factor and can be searched in the sub-database Journal Citation Reports. In medicine and science, the database generally has good exposure, while research in the humanities and social sciences sections is not as well represented.
How is a journal’s impact factor calculated?
In this example, we have chosen the 2018 Journal Impact Factor (JIF) for the journal Lancet. For 2018, the number of citations to articles from the Lancet in 2016 and 2017 is divided by the total number of published articles during the same two years, which gives the journal's impact factor.
About 2 per cent of the journals in Journal Citation Reports have an impact factor of 10 or higher. It is therefore relevant to compare journals in the same subject area.
One of the advantages of citation analysis is using large amounts of research, thus discovering patterns and deviations over time. It is imperative to compare apples with apples, that is, within the same subject area, the same annual interval, and the same publication type. This method is best suited for large units.
The journal I have chosen HAS an impact factor
In Journal Citation Reports – search for the title by entering the full name without abbreviations. Search results are presented with information about the impact factor and how often the journal is published, along with other information.
The journal I have chosen does NOT have an impact factor
Should a journal not be included in the sub-database Journal Citation reports, it may still be indexed in the Web of Science. This indicates that it is quality-checked and reviewed at least one year before assigning an impact factor. Via the Web of Science’s Master Journal List, search for the full name of the journal.
Open Access journals are indexed in the Web of Science. To see which are included in the Master Journal List, do a blank search (without typing something in the search box) and then narrow the search with Open Access in the left column. The database currently contains some 5,000 Open Access journals.