Electromechanical coupling coefficient (kt2) is an important parameter for determining the performances of RF BAW filters. According to the IEEE standard, the resonance-antiresonance method for a self-standing film structure is recommended to determine kt2 of the piezoelectric film. It is convenient and cost-effective to determine the kt2 from the film/wafer structure or epitaxial wafers. However, kt2 is underestimated due to the acoustic losses in the substrate in the conventional conversion loss method, which is powerful tool to extract the kt2 from HBAR. In this study, we introduce the conversion loss using electromagnetic signal including no acoustic losses.