The invention relates to a method for ascertaining a physical parameter of a gas using a measuring transducer having a measuring tube for conveying the gas, wherein the measuring tube is excitable to execute bending oscillations of different modes and eigenfrequencies, the method includes: ascertaining the eigenfrequency of the f1-mode and f3-mode; ascertaining preliminary density values for the gas based on the eigenfrequencies of the f1-mode and f3-mode; ascertaining a value for the velocity of sound of the gas, and/or, dependent on the velocity of sound and the eigenfrequency of a mode, at least one correcting term and/or density error for the preliminary density value; and/or a correcting term for a preliminary mass flow value for determining a corrected mass flow measured value based on the first preliminary density value, the second preliminary density value, the eigenfrequencies of the f1-mode and f3-mode.