This research studied the optimal design of shape memory alloy (SMA) muscle wire bundle actuators. Current literature describes the use of multiple muscle wires placed in parallel to increase the lifting capabilities of an SMA actuator, which however, is limited to wires of like-diameter. A constrained optimization problem was formulated, with constraints on the maximum number of wires, voltage applied, and SMA bundle length and cross-sectional area, that explored the use of several different diameter wires for the development of an optimal SMA bundle actuator that will be able to apply maximum force. As a case study, the optimal design of SMA bundle actuators for the Rutgers robotic hand is presented.