A method for designing a die surface of a die intended for forming a workpiece into a target formed part, comprising • generating a workpiece simulation-model corresponding to the workpiece, • generating a target simulation-model corresponding to a target formed part, • determining an initial die surface (30,30'), which an initial numerical simulation predicts as forming the workpiece simulation-model into the target simulation-model, • with a die having the initial die surface (30,30'), forming the workpiece into an actual formed part (20,20'), • by measuring the actual formed part (20,20'), generating a numerical representation of the actual formed part (20,20'), • based on the numerical representation of the actual formed part (20,20'), generating an actual simulation-model, • determining residual stresses resulting from forming the workpiece simulation-model into □ the target simulation-model or □ the actual simulation-model, wherein the residual stresses are determined as a plurality of stress tensors, and wherein each stress tensor is assigned to a location on or within □ the target simulation-model or □ the actual simulation-model • based on the stress tensors, providing weightings, wherein each weighting is assigned to a location on or within □ the target simulation-model or □ the actual simulation-model • based on the residual stresses, matching the actual simulation-model and the target simulation-model, • based on deviations between the matched target simulation-model and actual simulation-model, modifying the initial numerical simulation to provide a modified numerical simulation, and • determining a corrected die surface, which the modified numerical simulation predicts as forming the workpiece simulation-model into the target simulation-model, and • re-shaping the initial die surface with help of NC machines to arrive at the corrected die surface characterized in that matching the actual simulation-model and the target simulation-model comprises determining minimal deviations between the actual simulation-model and the target simulation-model under consideration of the weightings, such that the higher the weighting at a certain location is, the closer the actual simulation-model and the target simulation-model • generating a workpiece simulation-model corresponding to the workpiece, • generating a target simulation-model corresponding to a target formed part, • determining an initial die surface (30,30'), which an initial numerical simulation predicts as forming the workpiece simulation-model into the target simulation-model, • with a die having the initial die surface (30,30'), forming the workpiece into an actual formed part (20,20'), • by measuring the actual formed part (20,20'), generating a numerical representation of the actual formed part (20,20'), • based on the numerical representation of the actual formed part (20,20'), generating an actual simulation-model, • determining residual stresses resulting from forming the workpiece simulation-model into □ the target simulation-model or □ the actual simulation-model, wherein the residual stresses are determined as a plurality of stress tensors, and wherein each stress tensor is assigned to a location on or within □ the target simulation-model or □ the actual simulation-model □ the target simulation-model or □ the actual simulation-model, wherein the residual stresses are determined as a plurality of stress tensors, and wherein each stress tensor is assigned to a location on or within □ the target simulation-model or □ the actual simulation-model □ the target simulation-model or □ the actual simulation-model • based on the stress tensors, providing weightings, wherein each weighting is assigned to a location on or within □ the target simulation-model or □ the actual simulation-model □ the target simulation-model or □ the actual simulation-model • based on the residual stresses, matching the actual simulation-model and the target simulation-model, • based on deviations between the matched target simulation-model and actual simulation-model, modifying the initial numerical simulation to provide a modified numerical simulation, and • determining a corrected die surface, which the modified numerical simulation predicts as forming the workpiece simulation-model into the target simulation-model, and • re-shaping the initial die surface with help of NC machines to arrive at the corrected die surface