# h-index: quantifying the impact of publication

In recent years, the h-index has become a popular citation metric influencing a scientist’s research more than the impact factor. Despite this, the two metrics differ even if they have an impact on the research outcome. The h-index is named so after the physicist Jorge Eduardo Hirsch who invented it in 2005 for quantifying a researcher’s productivity in research based on publications.

Why is the h-index different from the impact factor?

The h-index is a quantitative measure to estimate an author’s scientific output based on the number of research articles published in a given year and their citations. On the contrary, the impact factor evaluates the journal’s reputation based on the total number of articles cited in the specific journal in the previous two years.

Hence, the impact factor measures the prestige of a journal, while the h-index measures the individual author’s research output.

How can the h-index be calculated?

The h-index can be defined as the total number of published papers (Np) of a researcher that have been cited a number of times (Nc) by each paper (j) over n number of years.

For example, if a researcher’s h-index is 9, it conveys that the researcher has published nine or more papers, for at least 9 of them have been cited nine times. Taking another example, if a scientist has published 23 articles, of which 16 have been cited 16 times at least, and then the scientist’s h-index is 16.

1. An easy-to-calculate measure and objective in nature.
2. A better accurate metric than the impact factor.
3. It combines the outcome and the impact of a researcher, hence scores based on single-number measures such as citations per paper, number of highly cited articles, and the total number of citations.
4. Exclusion of poorly cited articles and do not give an inaccurate inflated score.
5. Useful for senior scientists with good publication records displaying their research and its effects in a positive manner.