Leakage inductance is one of the most important aspects of transformer design. Herein, the calculation of the leakage inductance of core-type tape-wound transformers is considered in the context of a magnetic equivalent circuit-based analysis used to support optimization-based design. In optimization-based design, numerical efficiency is critical since 10(5)-10(6) evaluations may be conducted. Thus, this paper presents a computationally efficient method to compute leakage inductances. The method is based on analytical calculation of the field intensity using Ampere's law in the noncore regions of the devices. The predictions of the proposed method are shown to be more consistent with the predictions of a 3-D finite-element analysis than other documented approaches.