The invention relates to a method for operating a power tool, according to which a measuring device determines a winding resistance (RS) of a winding of an electric motor of the power tool. A test signal source applies a test signal (ip) to the winding during operation of the electric motor, a measuring unit records at least one measured value (Ud, id) as a reaction of the winding to the test signal (ip), and a control device determines the winding resistance (RS) while taking into consideration the measured value (Ud, id).