This paper presents a method to compute the parameters of a transformer model with saturation using the voltage and current waveforms of an inrush test and a no-load test. The transformer is modeled with their electric and magnetic equivalent circuits and a single-valued function that characterizes its non-linear magnetic behavior. A 3-kVA single-phase transformer and a 5-kVA three-phase three-legged transformer have been tested in the laboratory. The method to obtain the parameters of the non-linear flux–current relation that characterize the saturation has been described in the paper. The analytical function used to adjust the experimental measurements fits them very well.