This paper provides detailed analytical modelling and finite elements method (FEM) analysis of the medium frequency transformer (MFT) leakage inductance, as one of the key design factors governing the operation of galvanically isolated power electronics converters. Precise leakage inductance modeling in design stage is especially important for converter topologies based on resonant conversion where MFT is a part of a resonant circuit. A comprehensive analytical model that takes into account both the geometric and frequency effects on the given MFT leakage inductance is generated based on the transformer physical structure, thus allowing for optimisation of the MFT design with targeted equivalent circuit leakage inductance reference. The derived models are benchmarked to the measurement results on the developed MFT prototype.