The h-index is defined as "the number of papers with citation number ≥ h , as a useful index to characterize the scientific output of a researcher" (J.E. Hirsch, 2005). For example, an h-index of 28 means there are 28 publications that have 28 citation or more for each. The h-index measures the impact of a researcher or group of researchers rather than a journal.

Tools for measuring h-index:

  • Web of Science: library subscribed database

  • Scopus: library subscribed database

  • Google Scholar: free search engine

    Below is a screenshot of an example on Google Scholar:

    h-index in Google Scholar

Limitations of h-index:

  • Inconsistent values between Web of Science, Scopus, and Google Scholar due to different coverage among these resources.
  • Does not fairly evaluate the research impact of early career researchers.
  • No data available for researchers in some disciplines, e.g. Arts and Humanities. 
  • Cannot capture full impact of an author or a group of authors, as not all publications are indexed in the available tools.

Below is a short video for you to learn about the limitations of the h-index for early career researchers: