The h-index was developed in 2005 by Jorge Hirsch, a physicist at the University of California in San Diego. Hirsch's paper was published in PNAS.
In his paper Hirsch states "A scientist has index h if h of his/her Np papers have at least h citations each, and the other (Np − h) papers have no more than h citations each."
There is some disagreement about the validity of the h-index.
Source: H-index illustrated.(2012) FrontMatter, 22, 5. Retrieved from: https://appocsite2com.files.wordpress.com/2016/03/frontmatter-22.pdf
You can calculate the h-index yourself, or let one of these two databases do it for you.
Remember: for each of these databases the h-index will be based upon the information from the journals they index.
Many databases will tell you that article X has been cited N times by articles in its database. Be aware that this number is based only on the articles indexed by that database; there may be other journals that cite your article that aren't listed in that database. So always check more than one database
Consider the list below a starting place. Check to see if your favorite database or journal publisher offers this feature.
Each citation source produces slightly different results depending on the content and coverage of the source. This underscores the importance of using multiple citation sources to judge the true impact of an author's work. The search strategy should be broad and inclusive enough to accommodate the following pitfalls.
-Search results vary by database used.
-Search all permutations of the cited author's name: last name; last name, first and middle initials; last name and first initial.
-If someone is second or third author, search by the lead authors to locate the cited reference.
-Author names and titles in foreign languages and non-Roman script may require extra effort to determine their transcription or transliteration in each database.