This paper proposes an efficient analytical approach to calculate the inductor core loss for Pulse Width Modulation (PWM) converters with the aid of a pre-built, user-friendly core loss map. Loss map is the most practical approach to accurately estimate the core loss of an inductor exposed to PWM operation. To predict the inductor core loss, the inputs of the loss map needs to be retrieved from the steady-state inductor voltage/current waveforms. For estimation purpose, an analytical approach is proposed in this paper, which enables mathematical and simplified computation of the operating space and core loss of the inductor in a PWM converter. The proposed approach is developed for both 2-level and 3-level converters and then validated by experiments. The results indicate that a 3-level converter operates the same inductor with less core loss compared to a 2-level converter, when the maximum current ripple is kept equivalent by halving the switching frequency in the 3-level converter.