In this paper, it is shown that due to scale effects in micromilling, tool size is a key parameter to consider in parameter optimization for productivity in a high-speed, high-precision micromilling operation. In this preliminary study, a method is proposed to determine the optimal tool sizes for roughing and finishing cuts in a micromilling operation, and corresponding feedrate and spindle speed profiles to maximize productivity. An objective function is developed for minimization, subject to a set of constraints. This paper will develop the framework of the optimization method and will consider constraints for sufficient reduction of geometric errors and achievability under spindle speed power limitations in particular. An algorithm is presented to solve the objective function assuming use of a roughing tool and a finishing tool. A numerical case study is presented to illustrate the implementation of the method.