Abstract: A formula for calculating the forming load of gears in hot precision forging was studied. The formula of forming load for gear forging was deduced by introducing the tooth impact factor into the formula for forming load of closed upsetting. The formula for the tooth impact factor was fitted by the data got from FEM simulation of forging process, in which gears of module 1, 2, 3, 4 mm were forged. The effects of the following parameters on the precision forming load were analyzed based on the new forming load formula: the diameter of root circle and bore of the workpiece, the height of the workpiece, module and flow stress of the billet material. Some forging tests for gears were conducted and the data of forming load in literature was utilized to validate the validity of the formula, as well as the application scope. The formula was further deduced to calculate the dimension range of forged gears for the presses with different nominal pressure, which was of engineering significance.