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Web of Science: Using a Citation Database: The H-Index: Author Impact

The H-Index

The h-index attempts to take into account both an author's productivity (total number of publications) and the impact of his or her work (number of subsequent citing articles).1 An h-index of N indicates that a researcher has published at least N papers that have each been cited at least N times. 

The h-index is typically calculated based on a researcher’s entire body of work, going back to his or her first publication. It could also be calculated for a limited number of years, or for a journal, department, research group, etc.


Example: Consider this publication records for the following fictional doctors:
1. Dr. Smith has written 5 articles. 4 of them have been cited at least once, but only 3 of them have been cited 3 times or more, so Dr. Smith’s h-index is 3.

1st article

Cited 10 times

2nd article

Cited 3 times

3rd article

Cited 7 times

4th article

Cited 0 times

5th article

Cited 1 time

2. Dr. Yong has written 5 articles. All 5 articles have been cited 100 times or more. Dr. Yong's h-index is 5.
The h-index cannot be higher than the total number of articles.

3. Dr. Lopez has written 100 articles. Each article has been cited two times.  Dr. Lopez has an h-index of 2.
The h-index cannot be higher than the highest number of citations received by any article.

Anyone can calculate an h-index using information from the Web of Science or another citation database. Remember, though, that journal coverage and the completeness of citation information varies among databases. The citation data and, therefore, the h-index may vary depending on the database you use.