The Kleissner’s foundation, KL Felicitas, developed an Impact Assurance Classification with New Philanthropy Capital in order to encourage fund managers to determine not only if they are achieving market rate returns, but also to measure their impact. In this article, Tasman-Jones examines this question of how to measure impact. Lack of adequate data is often one of the major challenges in assessing impact; however, standardized metrics such as IRIS help to overcome these barriers.