•Simple Damage Energy Criterium for life prediction in multiaxial fatigue.•Through frequency domain a multiaxial stress state can be reduced.•Auto and cross power spectra are the fundamental mathematical functions to do this.•Comparison between theoretical predictions and experimental data. In this paper, a new, simple Damage Energy Criterium for life prediction in multiaxial fatigue, developed in the frequency domain, is described and verified. The first aim of this paper is to demonstrate that through a correct use of the energetic approach, developed in the frequency domain, it is possible to achieve an accurate result. The proposed theoretical procedure finds its conceptual foundation in the fact that the energy criterion cannot be directly applied to usual stress state in the time domain; however, with a simple passage it is possible to accurately reduce a multiaxial stress state to an equivalent uniaxial one. For this reason, this work will be characterized by analytical content and by substantial mathematical demonstrations. At the end, in order to verify the method and consolidate the general procedure, some experimental tests are used to corroborate the validity of this criterion. This proposal shows drastically simpler technique than any other proposed in current literature.