Small rotor performance is important for small multi-rotor unmanned aerial vehicles to extend their endurance and enhance their payload capacities. However, a detailed survey on small rotors has not been conducted, and the effect of changes in the Reynolds number from 104 to 105 on rotor performance is unclear. This study evaluated how the rotor hover performance of NACA 0012, NACA 6409, and flat plate-shaped blade rotors was affected by Reynolds number decreases for rotors from Reynolds numbers of 53,000 to 18,000. Furthermore, the performance of rotors with different numbers of blades was investigated in relation to the Reynolds number defined with a blade chord length maintaining constant rotor solidity. In this evaluation process, figure of merit was used to assess the hover performance. This experimental evaluation revealed a degradation trend of hover performance in the low Reynolds number region, and the potential of using three-blade rotors for small multi-rotor unmanned aerial vehicles was clarified.