ABSTRACTOften, order quantity decisions are made by purchasers facing a price schedule of quantity discounts. Traditional solution procedures have consisted of the evaluation of total cost at numerous price‐break points in search of the lowest total cost. This approach is tedious and not particularly informative, especially when one is faced with lengthy schedules.This paper presents a total setup lot‐sizing model that reduces the computations required to find the least‐total‐cost quantity, given parameters from a supplier's price schedule.The parameters are first obtained by simple regression (graphical or computer) and in themselves can provide valuable insight for the purchaser's decision making. A total setup lot‐sizing model is next developed to define a “critical interval” that contains the solution. The model and algorithm are tested under a variety of conditions. Their application offers the decision maker a convenient alternative to determine the best quantity to order from a tendered p