A measurement method is for determining core losses, which serve to produce magnetic circuits for electrical machines. In order to allow an accurate measurement that is as quick as possible, it is proposed that a magnetic coupling is produced between a measuring coil connected in a capacitor and a core to be measured, and the measuring coil is then acted upon by an alternating frequency in order to measure the resonant frequency of the resulting resonant circuit and/or the quality of the resulting resonant circuit as a measure of the core loss.