A new fatigue parameter is proposed, which provides a new way of thinking to assess fatigue damage problems. The complete stress state at a certain material point, i.e., taking into account any material plane at that point, is included in the method. The influence of tension and compression state and also the mean stress are also included. Some experiments with different materials and loading conditions are used to validate the capabilities of the proposed method. The results show that the method provides good predictions for axial cyclic and/or torsion cyclic conditions with zero or nonzero mean stresses, in-phase and out-of-phase, different shapes of the specimen, loading waveform and loading path.