As we continue to navigate the COVID-19 pandemic, people around the world often ask themselves the same question as they head into various buildings and scenarios: What changes can we make to reduce the risk of COVID-19 transmission? To help provide some insight into this question, the Harvard Healthy Buildings Program has released this beta version of the ASIMI (Aerosol and Surface Interaction Model for Infectious diseases) Tool for calculating the risk of COVID-19 transmission, which estimates potential infection risk based on several factors and transmission pathways. This tool is based on our peer-reviewed paper in the Proceedings of the National Academy of Sciences of the United States of America.