Business process redesign is one of the most powerful ways to boost business performance and to improve customer satisfaction (Limam Mansar & Reijers, 2005). A possible approach to business process redesign is using redesign best practices. A previous study identified a set of 29 different redesign best practices (Reijers, 2003). However, little is known about the exact impact of these redesign best practices on workflow performance. This study proposes an approach that can be used to quantify the impact of a business process redesign project on all dimensions of workflow performance. The approach consists of a large set of performance measures and a simulation toolkit. It supports the quantification of the impact of the implementation of redesign best practices, in order to determine what best practice or combination of best practices leads to the most favorable effect in a specific business process. The approach is developed based on a quantification project for the parallel best practice and is validated with two other quantification projects, namely for the knockout and triage best practices.