Prediction of forming forces in Incremental Sheet Forming (ISF) is specially important in the case of using adapted machinery not designed for the process. Moreover, forming force is an important indicator that can be monitored on-line and utilized for real time process control. Besides experimentation, simulations based on the Finite Element Method (FEM) have been utilized as a reliable source of process force data. Nevertheless, the long solution times required to simulate ISF renders difficult its inclusion into a process optimization chain. In consequence, models that predict the forces required to manufacture simple parts have appeared. This work begins with a review of forming force models available for Single Point Incremental Forming (SPIF). Then, an equation recently proposed in the literature is compared with published experimental results of SPIF under different working conditions. The same data is employed to verify our own FEM simulations. Finally, the above-mentioned formula and FEM simulation were applied to predict the forming force of Variable Wall Angle (VWA) geometries where available force information is limited. Besides the applicability assessment of the equation, results will supplement a future experimental campaign focused in modeling geometries of intermediate complexity level by means of Computational Intelligence methods.