The charge response of a force applied to piezoelectric stack actuators was characterized in the range of 0 N – 20 N for application in piezoelectric self-sensing. Results show linear behavior between ap-plied force and collected charge for both actuators tested in this study. One actuator exhibits a 3.55 times higher sensitivity slope than the other related to its larger capacitance. An error analysis reveals a reduction of relative error in charge measurement with rising forces applied to the actuators.