When it comes to power transformer design, the main challenge is to satisfy a list of operation specifications. This challenge is translated to identifying the transformer design details that would lead to the guarantee of meeting the required specifications. The novel contribution of this chapter is to present the details of an efficient and relatively accurate non-iterative specifications-oriented design methodology. According to this methodology, main specification requirements may be directly correlated to four main design parameters. More specifically, the transformer volt-ampere rating, the overall ohmic copper losses, the no-load losses, and the ohmic reactance per phase may be correlated to the transformer window height, the limb diameter, the maximum core flux density, and the average conductors’ current density. It should be pointed out that all other transformer design details may be deduced from the aforementioned design specifications and leading variables. Details of the proposed methodology are presented in the sections of this chapter.