The study analyzed the performance and estimated the optimum operating conditions of a peanutsizing machine prototype based on a counter-rotating cylinder pair, developed for small- and mediumsized enterprises. To this end, the tests were conducted to determine the performance and power consumption of the prototype. The performance tests were done at nine different mixture rates based on peanut size (small or medium) and over-all separating efficiency. The theoretical capacity of the machine was found to be 123, 234.8 and 321 kg h(-1) for small, medium and large-size peanuts, respectively. In the preliminary tests, the average damage percentage and feeding capacity were found to be 1.76% and 126.3 kg h(-1), respectively. The over-all efficiency of the peanut sizing machine decreased as the proportion of small peanuts in the material increased, with values ranging from 0.87 to 0.97. The power consumption of the separating cylinders ranged from 0.46 to 0.76 kW. The average torque value was also calculated as 25 Nm.