This paper aims at a new definition of complexity factor based on strain, peak load and die fill state using finite element method (FEM). Since complexity factor indicates the forging difficulty of cold forging parts, larger complexity factor means greater strain, higher peak load and tends to cause incomplete die fill. Various geometric profiles of parts have been discussed and the relationships of complexity factor and maximum effective strain, peak load and die fill were investigated by FEM. In comparison with the existing definition of complexity factor, the newly proposed complexity factor can reflect the forging difficulty more reasonably. (c) 2008 Elsevier Inc. All rights reserved.