We have adapted an analytical computer model, RMxprt, to predict the operating parameters of both single-phase and three-phase induction motors as a function of motor lamination material property curves. The model uses newly defined parameters, integrated average core loss (IACL) and integrated average permeability (IAP), rather than the material characteristic commonly used today, 1.5-T permeability, which is not effective in predicting motor efficiency. IACL and IAP have been shown to be excellent predictive parameters of the efficiency of motors, and these parameters are considered the best for specifying motor laminations. IACL is closely correlated with the 1.5-T core loss and IAP is closely correlated with the 1.0-T permeability and, for semiprocessed materials, the 1.5-T core loss. Therefore, the 1.5-T core loss alone can be used to specify semiprocessed cold-rolled motor lamination materials for motors. For all cases studied, directionally averaged IACL and IAP are almost the same as the L&T Epstein pack properties. Therefore, the L&T Epstein pack properties, obtained by conventional Epstein testing, can be used in lieu of the directionally averaged properties.