The most common and well known bibliometric is journal impact factor.

Impact factor measures the popularity of a journal. It cannot measure the quality or success of a journal.

Impact factor is calculated by taking the mean of citations of articles published in a journal in the past two (or five) years. For example:

• Journal A publishes ten articles per year.
• In 2020, each of those ten articles is cited once, meaning the yearly number of citations is 10.
• In 2021, each of those ten articles is cited twice, meaning the yearly number of citations of 20. 
• The impact factor for 2022 is calculated by dividing 30 (the total number of yearly citations over two years) by 20 (the number of articles published). That means for 2022, Journal A has an impact factor of 1.5.

Some of the highest impact factors in medicine are the Lancet (130.838), New England Journal of Medicine (91.245), and Journal of the American Medical Association (56.272). However, most impact factors are around 1. Generally, the wider the scope of the journal, the higher the impact factor is. A journal that focuses on a narrow field with few researchers, and therefore generates less research, will have a lower impact factor.

The h-index was created in 2005 by Jorge E. Hirsch at UC San Diego. It is calculated by determining that an author has published h papers that have been cited h number of times. For example:

• Author Brown has five publications.
  • Publication A has 9 citations, B has 5, C has 2, D has 2, and E has 1.
  • Author Brown's h-index is 2, because they have two publications with two or more citations. However, they do not have three publications with three or more citations. 
• Author Green has three publications.
  • Publication A has 3 citations, B has 3, and C has 4.
  • Author Green's h-index is 3, because they have three publications with three or more citations. 

h-index favors established researchers. Early career researchers will have less publications, and older articles have more opportunities to accrue citations. If Author White publishes five publications, their h-index may grow from one to five just through the passage of time. h-index also favors researchers in popular fields that generate a great number of articles, as well as fields where large numbers of citations per article are common. 

Altmetrics is a catch-all term for any alternative bibliometric measure to traditional bibliometrics like impact factors and h-index. Some examples of alternative measures include how many times an article is viewed, how many times the article is saved in citation databases like EndNote, or how how many times the article is shared on Twitter, Facebook, or other social media. 

Several services offer altmetric analyses, including Plum Analytics and Altmetric.com. However, there is no universal definition for what constitutes altmetrics, and altmetrics may be defined differently by different researchers.