The invention concerns a method for measuring a power (Pe, Pm) of an electric motor, that involves measuring a real current (I) of the motor, by means of a measurement sensor (11), the invention being characterised in that it involves inputting, on an interface (20), at least one piece of nominal power data (Pn), one piece of nominal speed data (Wn), one piece of nominal current data (In), one piece of nominal voltage data (Un), one piece of power factor data (cos φ) and the real current (I) of the engine, calculating, in the computer, a no-load current of the motor according to a first stored function depending on at least the data (Pn, In, Un, cos φ), calculating, in the computer, the active power (Pe) and/or the mechanical power (Pm) and/or the active energy and/or the mechanical energy according to at least one second stored function depending on at least the data (Pn, In), the real current (I) and the no-load current that has been calculated, and providing the power that has been calculated on an output interface (24).