The modeling of magnetic componentsfor use in electrical circuit simulation requires that the core material be accurately characterized. This paper investigates a method of extracting parameters to model the hysteresis behaviour of magnetic core materials and optimizing them to achieve accurateresults during circuit simulation. Metrics are defined to measure specific features of the behaviour of both the core magnetic material and the magnetic component, such as a transformer. This paper presents a method of applying these metrics for the purposes of comparison and optimization, and demonstrates the method using measured results and corresponding simulations. It compares the effectiveness of a weighted metrics function with that of a least squares goal function for the purposes of optimization. This paper suggests modifications to the original Jiles-Atherton model to improve the ability of the model to more accurately represent the behaviour of magnetic materials during saturation.