We have created an inventory to characterize the teaching practices used in science and mathematics courses. This inventory can aid instructors and departments in reflecting on their teaching. It has been tested with several hundred university instructors and courses from mathematics and four science disciplines. Most instructors complete the inventory in 10 min or less, and the results allow meaningful comparisons of the teaching used for the different courses and instructors within a department and across different departments. We also show how the inventory results can be used to gauge the extent of use of research-based teaching practices, and we illustrate this with the inventory results for five departments. These results show the high degree of discrimination provided by the inventory, as well as its effectiveness in tracking the increase in the use of research-based teaching practices.