The relative increment of the total flux in a secondary coil is presented as a function of sample magnetic susceptibility, a demagnetization factor, and the secondary coil filling factor caused by the sample. The filling factor was defined and its basic properties were given. The relation between the filling factor and geometric parameters of a spherical sample coaxially placed in a cylindrical coil was determined. The calibration factors, used up to now, and the filling factor, were compared. It was shown, that if the demagnetization factorD→1 (in the case of a thin film placed perpendicular to the magnetic field), and the sample susceptibility &khgr;≠−1, the magnetization susceptibility is not measurable, except in the case when &khgr;=−1.