Crystal plasticity-based numerical simulations help understand the local deformation behavior of multiphase materials. It is known that in full phase simulations, the local 2-dimensional (2D) representative volume elements (RVEs) results are distinctly different from 3-dimensional (3D) RVEs. In this work, the difference in the results of 2D and 3D RVEs is investigated systematically, and the effect of magnification, total strain and composition are analyzed. The 3D RVEs of dual-phase (DP)-steel are generated using DREAM-3D. The 2D RVEs are the sliced surfaces of corresponding 3D RVEs for a direct pixel-to-pixel comparison of results. It is shown that the corresponding 3D distribution can be rapidly derived from the 2D result based on the alternative error and least square method. The interactive parameters for these processes are identified and analyzed for the ferrite phase, which provides information about the convergence. Examined by qualitative and quantitative statistical analysis, it is shown that the corresponding 2D distribution by the fourth iteration has a prominent similarity with the exact 3D distribution. The work presented here contributes toward solving the paradox of comparing local strain from 2D crystal plasticity (CP) simulations with the effective 3D specimen used for tests.