Authors do not have impact factors, but journals do! Bibliometrics, H-Index, citation analysis, altmetrics, and researcher 'impact' are all terms for measuring an author's influence or impact on their respective fields.
The more works an author publishes and how many times the works are cited may indicate a 'higher impact' or prestige. In addition to these traditional methods, works and authors can also be measured by alternative metrics (altmetrics) such as: number of shares, tweets, likes, blogged abouts, etc.
Flow chart created by Hanna Schmillen, 2014.
It can take years for articles, books, etc. to get published, keep that in mind when tracking citations.
Page views and downloads are considered 'emerging metrics', but are quickly gaining acceptance, particularly as an early indicator of impact for articles. These metrics are sometimes available from individual publishers, including PLoS, Taylor & Francis, and Elsevier. Research networks including academia.edu, Mendeley, ResearchGate and SSRN (through its Ranking page), also offer readership and/or download metrics.
The h-index is calculated as follows - H stands for the number of articles that have each been cited H number of times.
So, an h-index of 30 means that the author has published 30 articles that have each been cited 30+ times.
Scopus and Google Scholar all calculate h-index based on their database of citations - the boxes below show how to get it from each source
Chart created by J. E. Hirsch, 2005.
Scopus will provide a host of author ranking information from the author search function. As you can see below, you can see the author ID information (including ORCID), total number of citations, h-index, documents/citations graph, and even link to co-authored works.
Google Scholar calculates not only h-index, but the i10-index for authors with a public profile which must created by the author. The i10-index is simply the number of articles with at least 10 citations.
In Google Scholar, searching for an author will pull up their profile as the first result. Clicking on the profile will bring you to their profile page, which includes both metrics, as seen below. For more information about creating a Google Scholar Profile and other ways to track your publications, see the Author ID & Scholarly Profile Tab.