When it comes to the computation / estimation of the switching losses in a multilevel converter, it is crucial to know the instantaneous value of the output current. If the average output current value is used instead, there is a non negligible error when the quality of the output current waveform is low. This paper addresses this issue with a generic and versatile fast numerical method for phase-disposition PWM that produces the exact switching pattern, hence the exact inductor flux, without having to run time-domain switched simulation(s), as the calculations are performed for the minimal set of points required to fully determine the inductor flux ripple at the switching instants.