A die face morphing concept was recently introduced for quick die design for evolutionary products from their prior generations. Based on this concept, this paper proposes a strain increment method for early formability assessment by predicting strain distribution directly from the part-to-part mapping process. This method consists of mapping the finite element mesh to the part geometry, solving a part-to-part mapping function with smoothness and strain gradient penalties, and extracting strain increment from geometric morphing. It is shown, through a case study, that the strain field estimated by the proposed strain increment method compares well with that from the direct finite element analysis. Since this method does not require the knowledge on new die surface, such formability assessment can serve as a tool for early manufacturing feasibility analysis on the new part design.