<p>This study investigates the critical factors influencing the die clamping force required for closed-die forging, particularly focusing on injector bodies and tripod units. A generalized semi-empirical formula was developed to calculate the required die clamping force by considering the material flow stress, contact area between the forging and die, and a newly introduced shape complexity factor. The shape complexity factor plays a crucial role in the accurate calculation of the die clamping forces, particularly for complex shapes. Experimental validation was conducted for the injector bodies and tripod shafts, and the calculated die clamping forces were compared with the experimental results. The findings show a strong correlation, confirming the reliability of the proposed formula. For instance, the die clamping force requirements for injector body-I, injector body-II, and tripod unit-II forgings were observed to increase with the stroke during forging, aligning with the theoretical predictions. Finally, to verify the reliability of the die clamping force calculation formula, the required die clamping forces for the closed-die forging of injector body-III and tripod unit-III were calculated in practical applications. These calculations were compared with existing methods and finite-element simulation results. Experiments were conducted using the calculated die clamping forces, resulting in well-filled forgings without flashes, thereby validating the effectiveness of the proposed method.</p>