Abstract: A device for measuring the amount flowing through and/or the speed of flow of a medium which is pumped by means of a pump unit. The device comprises a drive motor for producing the working cycles of the pump unit and a pick-off to detect said working cycles and to deliver a pick-off signal depending on said working cycles. Further included is an electronic unit (10) to record, by means of said pick-off signal, a value proportional to the number of working cycles. From this value, the amount flowing through and/or the speed of flow can be determined by means of a nominal calibrating factor K.sub.N laid down for the pump unit. The electronic unit 10 includes a calibrating unit 11 which is adjustable to convert said pick-off signal into at least one output signal which represents a certain true calibrating factor K.sub.V, calculated with reference to a specific correction factor K.sub.K for correction of the nominal calibrating factor K.sub.N.