The Metrics Toolkit is an open access resource aimed at helping researchers and evaluators understand and responsibly use research metrics, including bibliometrics and altmetrics. The Toolkit provides evidence-based information about research metrics across disciplines, including how each metric is calculated, where it can be found, and how it should (and should not) be applied. It can be used to learn about specific metrics, and also to choose appropriate metrics based on the type of impact you want to demonstrate, the research output you’re gathering data for, and the discipline of the work.