Adjustment of loop-powered pneumatic process control device interfaces is disclosed. A disclosed example interface for use with a pneumatic process control device includes a power input to scavenge power from a loop power control signal associated with the process control system, a movement controller to cause movement of an actuator powered by the loop power, where the actuator is operatively coupled to a movable control input associated with the process control device, and a calibrator to read position feedback of the actuator during the movement to calculate a positional error, where the calibrator is to adjust a set point of the loop power control signal based on the positional error to control the actuator.