Permanent magnet synchronous motors (PMSMs) are commonly used in electric vehicles because they have specific advantages such as high power density, high torque, and high efficiency. This paper presents the design of an interior permanent magnet (IPM) rotor motor with 5kw capacity as an electric motorcycle propulsion machine. Principal design calculations obtain initial design parameters. The choice of using a magnet dimension has a significant impact on performance. Optimization is applied to achieve the required torque characteristics by varying the permanent magnet size with fixed volume and length. The simulation is performed using finite element analysis software to obtain the speed and torque characteristics. The results showed that the motor torque was higher with a wider magnet scale and fewer magnets per pole. Furthermore, using thicker magnets obtained better motor efficiency. Hence, this needs to be taken into consideration when designing the motor according to torque specifications.