A numerical algorithm is proposed which is suitable to calc. the magnetic field distribution as well as the corresponding NMR time signals and frequency spectra induced by susceptibility effects. It accounts for a wide variety of system parameters such as various sample geometries, free and hindered self-diffusion, inhomogeneous susceptibility, and variable spin concn. It is suitable to cover multiple exptl. conditions such as single pulses, echoes, sample spinning at any tilt angle, and field gradient expts. Typical results are shown that demonstrate the sep. and combined influences of self-diffusion and sample spinning on spectral line shapes. Calcd. frequency shifts are compared with known anal. expressions and with exptl. data on dispersions of magnetic nanoparticles.