A method for calculating the power consumption of a mobile device, particularly of a mobile station of a mobile radio system, in an observation period .DELTA.t based on various possible system states s.sub.k in which the device can be in the period .DELTA.t. A value of a quantity .DELTA..sub.k is determined system-state-dependently for the system states s.sub.k occurring in the period .DELTA.t. The power consumption in the period .DELTA.t is calculated in such a manner that the quantities .DELTA..sub.k and state-dependent typical currents i.sub.k are taken into consideration.