We propose a Helicoidal Transformation for 2D Finite Element Method (FEM) calculation of AC losses in twisted conductors. The method is based on a helicoidal change of variables to transform the originally 3D problem into an equivalent 2D problem. For obtaining the critical state in superconductor we use the h-φ-formulation and E-J power law. The method is well suited for geometries with a helicoidal symmetry and we present the magnetic response and Joule losses of multifilamentary twisted wire in conducting matrix and CORC cable with a non-conducting core