Size grading is an important operation in food processing for the onion export industry in particular. The aim of this work was to develop an appropriate machine for sizing onions, reduce losses and reduce grading costs. Maximum sizing efficiency obtained was 94.9±2.82 % at zero longitudinal angle and at a belt speed of (0.23 m/s), while it was 94.5±3.69% at 10o longitudinal angle for the same belt speed. The overall average of the sizing efficiency (94.33%) was recorded at 20o side angle and the highest grading capacity (1.72 t/h) was obtained at 10o side angle and 10o longitudinal angle. Total costs of grading the produce were 3.89 LE/t. (0.7 US$/t). This machine has the potential to size other crops like potatoes, tomatoes, apples and citrus fruits. Keywords: onion grading, grading capacity, sizing efficiency, onion bulbs.