Two optimal design methods are proposed for the dimensional design of parallel manipulators, considering their dynamic performance over the desired ranges of motions, velocities, and accelerations. The first method, termed as the extrinsic method, directly minimises the actuator forces/torques within the desired safe working zone of the manipulator, for typical velocities and accelerations of the end-effector. The second method, namely, the intrinsic method, minimises a measure of the manipulator's inertia, as reflected at the actuators, over the said safe working zone. Case studies on the design of 3-RRR and 3-RRS manipulators are presented to illustrate the proposed methods. Numerical studies show that the optimal link dimensions obtained through these conceptually disparate methods are fairly similar. Naturally, the dynamic performances of the resulting manipulators are also comparable, which are found to be significantly better than that of arbitrary designs respecting the same constraints. © 2019 Elsevier Ltd