In recent years, considerable research has been directed towards the development of methods for designing families of products. In this paper, we present a Variation-Based Platform Design Methodology (VBPDM), which aims to satisfy a range of performance requirements using the smallest variation of the product designs in the family. In the first stage of the VBPDM, the common product platform around which the product family is to be developed is identified. A ranged set of solutions is found, represented by the mean and standard deviation of the input design variables, to meet a range of the different performance requirements for the product family. During this first stage, a compromise Decision Support Problem (DSP) is used to optimize the commonality goal that seeks to minimize the deviation of the input design variables, while satisfying the range of performance requirements. Those design variables that show small deviations are held constant to form the product platform. In the second stage of the VBPDM, each individual product is designed around the common platform such that the functional requirements of the product are best satisfied. As an example, the proposed method is used to develop a family of universal electric motors designed to meet a range of torque requirements. The results are compared against previous work.