The physical and mechanical behaviour of onion differs for each variety. Especially for proper handling and storage of the onion is quite important for preventing the quality loss and plant damage. In this research the dimensional analysis and buckingham Pi Theorem was applied to predict crushing forces of Banko and Yalova 12 onion varieties. Dimensionless pi terms were developed using measured vertical forces, deformation, diameter of the onion, failure strain energy, and modulus of elasticity of onions. The crushing force were predicted with linear correlation value of 0.898.