There are many excellent guides on measuring research impact and related topics. Two of these guides were especially influential in the creation of this guide:
Why measure or track research impact?
While there are many reasons to measure research impact, there has not been universal agreement on how to do so. Additionally, as methods of scholarly communication expand beyond the traditional journal article, existing metrics become less relevant. New metrics continue to be developed in attempts to improve upon existing measures.
This guide covers some of the more common measures of author, journal, and article impact - what they are, and how to find them. It also covers new metrics that go beyond published journal articles. Finally, it gives tips on how to broaden the impact of your research.