Citation index numbers provide a way to measure impact beyond raw citation counts. Index numbers can be calculated for individual articles, a group/list of publications, or even all the articles published in a journal or field (see our Journal Impact page).
What is the "best" index number?
Generally, the "best" measurement depends on what matters to you. The h-index is the most widely known index measurement. Some alternative measurements, like the g-index, address specific issues with the h-index. Other measurements target recent publications and citations, such as the the contemporary h-index.
Other Citation Index Numbers
Alternatives to the h-index include:
g-index: Gives more weight to highly cited publications. The original h-index is insensitive to high "outliers" -- a few papers that have very high citation counts will not sway the h-index score (much). The g-index allows highly cited papers to play a larger role in the index, and tends to emphasize visibility and "lifetime achievement."
hc-index (contemporary h-index): Gives more weight to recent publications. The original h-index favors senior researchers with extensive publication records, even if they have ceased publishing. The hc-index attempts to correct this and favors researchers currently publishing.
i10-index: Measures the number of papers that have at least 10 citations. Introduced (and used) by Google Scholar.
m-quotient: Divides the h-index by the number of years since the researcher's first published paper. m-quotient was proposed as a way to help younger researchers who may not have long publication lists.
Web of Science or Google Scholar will automatically calculate the h-index for the list of publications in your profile.
Publish or Perish will calculate h-index (and many other index numbers) for an author's publications.
If you want to calculate an h-index manually, Hirsch defines the h-index as follows: "A scientist has index h if h of his or her Np papers have at least h citations each and the other (Np – h) papers have ≤h citations each."