An onion size grader for common onion with capacity of 2 ton/h was developed. It has the components namely i) feeding chute, ii) grading drum, iii) collection chute and iv) power transmission system. The grader has three portions in which cushioned rods were mounted with a constant gap to grade onion less than 40 mm, 40.1 – 60 mm and 60.1 – 75 mm. The oversize onions greater than 75.1 mm size are collected at the other end of grading drum whereas, other three grades are collected through the cushioned outlets mounted below the grading drum. One 2 hp geared motor with 50 rpm speed and four rollers mounted on the frame used to rotate the grading drum. The cost of grading was 10 times lower than manual grading.