The undershot waterwheel is recommended to increase electrification ratio in remote areas of Indonesia due to its simple shape, which results in higher efficiency under low head conditions than other turbines. Using analytic and numerical methods, this study develops an equation to determine how many blades should be used and examines the effects of the kinetic energy of water on the energy conversion process to determine how the undershot waterwheel should be classified. Analytical methods were used to develop an equation to determine blades number, and numerical methods were used to verify the new equation. Variable inlet velocities of 1 m/s, 3 m/s, and 5 m/s and variations in blades number of 6, 7, 8, 9, and 10 blades were tested. From the analytical results, the recommended blades number is 8. Based on the numerical results, an 8-bladed waterwheel is most efficient with variable inlet velocities of 1 m/s (45.58% efficiency) and 5 m/s (13.84% efficiency). Analyzing the data using two-factor analysis of variance (ANOVA) without replication, it was determined that blades number effects output power, but inlet velocity does not. Thus, the proposed equation for determining the ideal blades number can be effectively used, but it still needs validation through experimentation. Furthermore, the kinetic energy of water was not found to have an effect on the energy conversion process in an undershot waterwheel, therefore, the undershot waterwheel should be classified as a reaction turbine.