In this paper, we propose an analytical method to compute the eddy-current loss in nonlinear thick steel laminations (3-12 mm) by considering the return path of the eddy currents. Initially, a 2D finite-element (FE) model is applied to segregate losses measured from toroidal material samples into hysteresis and eddy-current loss components to use them as reference. Afterwards, a 2D analytical time-domain model is proposed for the eddy currents based on the solution of the 2D field problem. The time-domain model is then used to derive a simple frequency-domain eddy-current loss formulation for the sinusoidal flux density case with the inclusion of a skin-effect correction factor, which accounts for the nonlinearity of the material. Highly accurate results are obtained from the proposed model compared to FE reference results with a mean relative error of 5.1% in the nonlinear region.