A method for calibrating a radiometric device for determining and/or monitoring the density of a medium located in a container includes: determining the count rate of the radioactive radiation after it has passed through the empty container on the basis of the activity of the transmitting unit; determining the measured count rate of the radioactive radiation after it has passed through the container when a calibration medium of known density is located in the container; determining the mass attenuation coefficient according to the formula μ=−(ln(N/N0))/(ρ1D), where D is a beam path of the radioactive radiation or inner diameter of the container, and ρ1 is density of the calibration medium; and calculating a calibration curve representing the dependence of the density of the medium on the count rate of the measured radiation intensity after the radiation has passed through the container.