The term impact factor was first coined by Eugene Garfield in the year 1955.His aim was to select journals for Science Citation Index (SCI) based on the quality rather than size of the journal. For eg., there are few smaller but important journals, they will never be selected for SCI if only number of citation or publication count is been done.
The 2016 impact factor of a journal would be calculated as follows:
2016 impact factor = Y/C
Y = the number of times that all items published in that journal in 2014 and 2015 were cited by indexed publications during 2016.
C = the total number of "citable items" published by that journal in 2014 and 2015. ("Citable items" for this calculation are usually articles, reviews, proceedings, or notes; not editorials or letters to the editor).
Provides a reflecting tools for ranking, categorizing, evaluating, and comparing various International/National Journals having ISSN published by Learning societies Universities and Institutions & Publication house.
This factor is used for evaluating the prestige of journals. The evaluation is carried out by considering different the factors like Peer Review, Originality of Content, Technical editing quality, editorial quality etc.
Thus, the impact factor of a journal is calculated by dividing the number of current year citations to the source items published in that journal during the previous years. The impact factor is a very useful tool for evaluation of journals, but it must be used discreetly.