The present disclosure relates to a Coriolis mass flow meter including: a measuring tube; an one exciter for generating vibrations in the measuring tube; two sensors for detecting the vibrations in the measuring tube and for outputting associated sensor signals; and an operating and evaluating unit for determining a mass flow value of a medium in the measuring tube based on a phase difference or time difference between the sensor signals, wherein for Reynolds numbers below a Reynolds number threshold a cross-sensitivity to a viscosity of the medium correlates with a Stokes number, wherein the operating and evaluating unit is configured to determine a current value of the Stokes number for Reynolds numbers below the lower Reynolds number threshold and to compensate for the influence of the cross-sensitivity in the determining of the mass flow.