Method for the quantitative determination of the mass of the content of closed foil packages, wherein each of the individual foil packages has a metallic foil layer (4, 5) and filling spaces with a base surface, the method comprising the following procedural steps: - in a calibration routine at least one closed first reference package without content is x-rayed by means of an x-ray source and a first set of initial x-ray images is produced therefrom; - a mass calibration signature is derived from the first set of initial x-ray images; - at least one closed second reference package with a reference content is x-rayed by means of the x-ray source and a second set of initial x-ray images is produced therefrom; - an initial reference signature is derived from the second set of initial x-ray images; - a reference measured value is derived from the initial reference signature and the mass calibration signature; - the mass of the reference content of the at least one second reference package is quantitatively determined as reference mass by weighing and assigned to the reference measured value; - the calibration routine is terminated, followed by an ongoing measuring operation; - in the ongoing measuring operation closed foil packages with a content each are x-rayed by means of the x-ray source and at least one set of measuring x-ray images is produced therefrom; - in the at least one set of measuring x-ray images, a first composite signal is determined and linearised within the base surface and a second composite signal is determined and linearised in a marginal region of the foil package outside the base surface, wherein a measurement signature is determined by differentiation between the first and the second composite signal; - from the measurement signature and the mass calibration signature, measured values are derived for the individual closed foil packages by differentiation; - from the measured values, the masses of the contents of the closed foil packages are quantitatively determined, taking account of the assignment of the reference mass to the reference measured value. - in a calibration routine at least one closed first reference package without content is x-rayed by means of an x-ray source and a first set of initial x-ray images is produced therefrom; - a mass calibration signature is derived from the first set of initial x-ray images; - at least one closed second reference package with a reference content is x-rayed by means of the x-ray source and a second set of initial x-ray images is produced therefrom; - an initial reference signature is derived from the second set of initial x-ray images; - a reference measured value is derived from the initial reference signature and the mass calibration signature; - the mass of the reference content of the at least one second reference package is quantitatively determined as reference mass by weighing and assigned to the reference measured value; - the calibration routine is terminated, followed by an ongoing measuring operation; - in the ongoing measuring operation closed foil packages with a content each are x-rayed by means of the x-ray source and at least one set of measuring x-ray images is produced therefrom; - in the at least one set of measuring x-ray images, a first composite signal is determined and linearised within the base surface and a second composite signal is determined and linearised in a marginal region of the foil package outside the base surface, wherein a measurement signature is determined by differentiation between the first and the second composite signal; - from the measurement signature and the mass calibration signature, measured values are derived for the individual closed foil packages by differentiation; - from the measured values, the masses of the contents of the closed foil packages are quantitatively determined, taking account of the assignment of the reference mass to the reference measured value.