This paper describes an scalable Planar-Square One-turn Inductor model valid for estimating the quality factor and the input impedance of the inductor up to its self-resonance frequency (SRF). Therefore it can be used to guide the optimized process of the inductive link and the power stage of the WPT system without full-wave electromagnetic simulation. The proposed scalar model is analytic, its circuit components have physical meaning, and its model parameters can be extracted from empirical or simulated data. This model was assessed by full-wave EM simulation, the results was consistent the values predicted by the lumped model.