The objective of this paper is to develop an analytical optimal design tool to determine a megawatt-scale yokelss and segmented armature (YASA) machine design that fulfills the application requirements and constraints. This analytical tool considers both electromagnetic and structural designs. Different designs that provide similar performance will have emerged from this analytical process. A design reference map that graphically shows the relationships and tradeoffs between each objective function is introduced. A multicriteria optimization process is applied to determine a design optimum. In the optimization process, the design objectives considered in this study are to minimize the outer diameter, to minimize the structural mass of the machine, to minimize the copper and iron losses, and to minimize the active materials cost. Three variables considered in calculating the objective functions are the air-gap flux density, the ratio of outer-to-inner machine diameter, and the current loading. The optimization method uses a pseudoweight vector to provide the flexibility to prioritize one or more objective functions, dependant on the specific application requirements.