The g-index is an author-level metrics suggested in 2006 by Leo Egghe.

The index is calculated based on the distribution of citations received by a given researcher's publications, such that given a set of articles ranked in decreasing order of the number of citations that they received, the g-index is the unique largest number such that the top g articles received together at least g2 citations. Hence, a g-index of 10 indicates that the top 10 publications of an author have been cited at least 100 times (102), and a g-index of 20 indicates that the top 20 publications of an author have been cited 400 times (202).