This paper focuses on optimizing the static order batching problem (OBP) with multiple pickers. This problem involves optimal assignment of a set of customer orders to batches, given capacity constraints, in order to minimize the total distance travelled. The order picking strategy considered is cluster picking. We assume that each picker is assigned one batch and all pickers begin the pick tour simultaneously. The aim is to minimize the total distance travelled by all pickers, which is calculated based on the S-shape routing strategy. A mathematical model is developed to solve the OBP for small-scale instances. For larger instances, a simplified version of an order batching heuristic proposed by DHL Supply Chain is utilized and experimented with for different-sized problems. Both approaches are compared to the conventional first come first serve (FCFS) method of order batching.