The conventional design technique of transformer cores and yokes remains fundamental in ensuring optimal performance, efficiency, and cost-effectiveness of electrical transformers. This chapter explores the traditional methodology applied to the core and yoke design, considering both core-type and shell-type transformer configurations. Central to the design process is the selection of volts per turn, which directly influences the core cross-sectional area and the overall dimensions of the magnetic circuit. The flux density is carefully chosen within permissible limits to ensure minimal core losses while maintaining magnetic efficiency. Likewise, current density is selected based on thermal constraints and economic factors to achieve a balanced compromise between copper loss and conductor size. Emphasis is placed on the geometry of the core, with particular attention given to square and stepped core arrangements to optimize space and reduce leakage flux. The window and core proportions are determined to meet both electrical and mechanical design requirements, providing adequate space for windings while maintaining magnetic integrity. Lastly, the yoke design is addressed to ensure uniform flux distribution and structural stability, completing the magnetic circuit with minimal reluctance. The conventional design approach, though manual and iterative, offers valuable insights into transformer behavior and design optimization.