Developing a robust, product platform architecture brings an important competitive advantage to a company. The major benefit is reduced design effort and time-to-market for future generations of the product. This paper describes a step-by-step method that aids companies in developing such a product platform architecture. Using the concept of specification “flows” within a product development project, the design for variety (DFV) method develops two indices to measure a product’s architecture. The first index is the Generational Variety Index (GVI), a measure for the amount of redesign effort required for future designs of the product. The second index is the Coupling Index (CI), a measure of the coupling among the product components. The design team uses these two indices to develop a decoupled architecture that requires less design effort for follow-on products.