In this paper, a novel methodology is presented in order to design a permanent magnet synchronous machine associated with a gearbox for a screwdriver application. The study shows how, from specification such as maximum volume, maximum heating, torque, and speed profiles, it is possible to formulate the sizing problem. The modeling is based on a purely analytical formulation. We will show that it is possible to establish rules in order to make optimal choices of materials (magnets and stator core). The optimization of the pole pair number and the choice of the gear ratio will also be discussed. Finally, the finite element method will be used to validate the designed machine.