The h-index has become a leading metric for evaluating an author’s impact through published work. Developed in 2005 by J.E. Hirsch at the University of California, San Diego (Hirsch, 2005), the h-index was proposed as an improvement over traditional metrics such as total number of papers, total citations, or average citations per paper. Hirsch argued that these earlier measures failed to capture a researcher’s true influence. The h-index addresses this by ranking an author’s publications in descending order by citation count; the h is the number of papers that have been cited at least h times.
In the table below, the articles are listed in descending order of citation count. The h-index is 93 (see highlighted section) because at least 93 articles have each been cited 93 times.
In this example, the document number and citation count are the same, though this will not always be the case. For instance, if document 93 had only 92 citations, the h-index would be 92. This is because the h-index (h) is defined as the number of publications (N) that have each been cited at least h times.
Alternatively, you can create a chart comparing the number of documents to their citation counts and identify the point where the document number equals the number of citations—this intersection represents the h-index.
The idea behind the h-index was to create a simple, easy-to-understand metric that could quantify a researcher's output and impact. It has remained popular over time for several reasons:
It condenses productivity and impact into a single number
It does not require a minimum number of publications
It avoids the need for arbitrary thresholds
It is easy to interpret
It offers a relatively robust measure of a researcher’s influence
However, the h-index is not without its limitations. It can be inflated by factors such as a high average number of co-authors per paper, excessive self-citations, or continued citations of older articles. This means a researcher’s h-index may keep increasing even after they stop publishing—or even after they pass away.
There are a few ways to determine your h-index. However, depending on the method, you will get a different number, so always remember to cite where you found your h-index. The three major locations for an h-index are Scopus, Web of Science, and Google Scholar.