A method for determining the compressibility of a flowing fluid, the method comprising the following steps: Driving a volumetric flow of the fluid by means of a pump, through at least one measuring tube of a vibronic density meter at a first pressure maintained by means of a throttle, a first pressure sensor and a second pressure sensor being arranged between the pump and the throttle, the density meter being arranged between the first pressure sensor and the second pressure sensor; Determining a first density measurement of the flowing fluid at the first pressure; Determining a first measured pressure value of the flowing fluid at the first pressure; Driving a volume flow of the flowing fluid by means of a pump, through a density meter at a second pressure which is maintained by means of a throttle; Determining a second density reading of the fluid at the second pressure, which is different from the first pressure; Determining a second measured pressure value of the flowing fluid at the second pressure; Determining the compressibility of the fluid, using the first density measurement value, the second density measurement value, the first pressure measurement value and the second pressure measurement value, assuming that the composition of the fluid is unchanged between the detection of the first density measurement value and the second density measurement value, characterized in that the volume flow is a defined volume flow which is driven by a dosing pump with a delivery accuracy of better than 1%, in particular better than 0.5%, the pressure drop across the density meter is calculated by forming a difference between the measured pressure values of the first pressure sen sensor and the second pressure sensor, and a viscosity of the fluid is determined on the basis of the volume flow and the pressure drop, whereby the measured density value of the vibro nical density meter is corrected with regard to a cross-sensitivity to the viscosity of the fluid. Driving a volumetric flow of the fluid by means of a pump, through at least one measuring tube of a vibronic density meter at a first pressure maintained by means of a throttle, a first pressure sensor and a second pressure sensor being arranged between the pump and the throttle, the density meter being arranged between the first pressure sensor and the second pressure sensor; Determining a first density measurement of the flowing fluid at the first pressure; Determining a first measured pressure value of the flowing fluid at the first pressure; Driving a volume flow of the flowing fluid by means of a pump, through a density meter at a second pressure which is maintained by means of a throttle; Determining a second density reading of the fluid at the second pressure, which is different from the first pressure; Determining a second measured pressure value of the flowing fluid at the second pressure; Determining the compressibility of the fluid, using the first density measurement value, the second density measurement value, the first pressure measurement value and the second pressure measurement value, assuming that the composition of the fluid is unchanged between the detection of the first density measurement value and the second density measurement value, characterized in that the volume flow is a defined volume flow which is driven by a dosing pump with a delivery accuracy of better than 1%, in particular better than 0.5%, the pressure drop across the density meter is calculated by forming a difference between the measured pressure values of the first pressure sen sensor and the second pressure sensor, and a viscosity of the fluid is determined on the basis of the volume flow and the pressure drop, whereby the measured density value of the vibro nical density meter is corrected with regard to a cross-sensitivity to the viscosity of the fluid.