This work deals with a method of analysis which estimates the increase of core losses under sinusoidal and nonsinusoidal inductions. The estimation can be carried out by correlating instantaneous magnetization power (P-M) Or the instantaneous magnetic field (H) as a function of the magnetization rate (dB/dt) and the induction level (B). Experimentally, this correlation can be obtained under triangular waveform induction tests. Predictions under sinusoidal and nonsinusoidal inductions were made in oriented and nonoriented FeSi steel sheets, The predictions, when compared to experimental results, show an error of up to 3% for nonoriented, and of up to 5% for oriented materials. Also, this method allows the prediction of the loss loop shapes, The limitations and perspectives of the method are considered in this work.