The difficulty of obtaining a useful cost estimate at the design stage has long been acknowledged. Data for new products are hardly available and product specifications are often expressed as a range of values; yet, only limited progress has been made to date to improve the quality of the average cost estimate at the conceptual design stage. The aim of this research is to improve the quality of the cost estimate (average cost) at the conceptual stage of design to assist designers to consider cost as a critical factor in selecting the most appropriate design concept. This research investigates the use of Taguchi’s orthogonal array approach to reduce the variation in the product specification (when expressed as a range of values) in order to improve the quality of the average estimated cost for each concept at the conceptual stage of design. A new process has been created, and to validate the process, an industrial case study has been undertaken.