This paper proposes a novel iron loss calculation method based on the loss-map of the magnetic materials. The distinctive feature of this method is that the iron loss on the inductors in many kinds of converters can easily be calculated even if the magnetizing conditions of the inductors are different. In this paper, the dynamic minor loop characteristics of the magnetic core on the condition of the switching converter are defined. Then, the dynamic measuring method of the dynamic minor loop by using the chopper circuit is presented. Next, some typical loss characteristics derived from the dynamic minor loop measurement is discussed. Also, a novel loss calculation method of the ac filter inductor on the PWM inverter by using the modified loss-map method is proposed.