Publish or Perish is free, downloadable software that uses data from Google Scholar to calculate a variety of metrics, beyond just the h-index
An author's impact on their field or discipline has traditionally been measured using the number of academic publications authored and the number of times these publications are cited by other researchers.
There is an increasing number of author level metrics to choose from, but publication count and h-index are two of the better-known metrics.
One of the most widely used measures is the h-index, which measures both quantity (number of publications) and quality (number of citations).
To calculate an h-index, you count the number of publications by an author that have been cited at least the same number of times
Example: An author has published 4 papers:
Paper 1 has been cited 10 times
Paper 2 has been cited 100 times
Paper 3 has been cited 5 times
Paper 4 has been cited 2 times
In this scenario, the author would have an h-index of 3, because of the author's 4 papers, 3 have been cited at least 3 times.
An h-index of 3 means that an author has 3 papers that have each received at least 3 citations.
A common criticism of the h-index is that it is not an accurate measure for early-career researchers.
Google Scholar Profile - once you've created a profile, it is easy to add publications and see your h-index. However, you should check data in Google Scholar carefully, since it can be more prone to errors and duplication.
Web of Science (only available through an institutional subscription) is a large, interdisciplinary database that tracks citations. One way to view your author metrics in Web of Science is to register for ResearcherID and add publications to your author profile (using ORCID, EndNote, Web of Science, etc.).
Scopus (only available through an institutional subscription) is a multi-disciplinary database that indexes journal articles, conference publications, and more. Complete citation data is available from 1996 to present, so citation data prior to 1996 may be incomplete.
Note: Because databases like Web of Science, Scopus, and Google Scholar differ in the content that they include, it is likely that your citation counts, and even your h-index, will be different depending on which database you use.