For the calculation of shaft eigenfrequencies, the Campbell diagram is a very helpful tool for better understanding the critical speed of a shaft (module WA4). In KISSsoft, the Campbell diagram can be calculated for a desired speed range. It presents the eigenfrequencies and critical speeds. The calculations are possible for coaxial shafts as well. The results obtained provide a very reliable accordance with the relevant literature on machine dynamics or the 'Jeffcott rotor'. The actual eigenfrequency calculation in KISSsoft allows the consideration of either non-linear or anisotropic bearing stiffness and spinning effect.