Knowledge of the physical properties of date fruit is necessary for the design of postharvesting equipment such as cleaning, sorting, grading, kernel removing, and packing. Also, the physical and mechanical properties are incorporated in the development of the grading machine as a case study. In this study, some physical and mechanical properties of three mandarin cultivars, as promising fruits, were analyzed to help the design of handling machines. According to results, the greatest dimensional characteristics were found for Page cultivar, whereas Onsho cultivar showed the lowest sphericity value (93%), and the highest sphericity was observed in Clementine cultivar (97%). The specific gravity of Page cultivar was 0/97, and this cultivar had the biggest fruit. Thus, it may be used for export. The volume measured was 1% higher than the calculated assumed shape of the spheroid . The relationship between diameters and mass was linear, and the correlation was high for all studied cultivars and mixed cultivar (combined all data). There was a linear relation between mass and volume of the mixed cultivar of mandarin with a high coefficient of determination. 1. Introduction Citrus are the major horticultural crops in Iran so that this country has a high annual production level of citrus fruit and was ranked the 15th producer in the world [1, 2]. The mandarin (Citrus reticulata) is a species of citrus fruit that is an evergreen tree (like other trees of this family) and slow growing. Mandarin begins to bear fruit when it is around three years old. Iranian mandarins are not exported because of variability in size and shape and lack of proper packaging [3]. Consumers prefer fruits with equal weight and uniform shape. Mass grading of fruit can reduce packaging and transportation costs and also may provide an optimum packaging configuration [4]. Fruit crops and food products have several unique characteristics which set them different from engineering materials. These properties determine the quality of the fruit, and identification of correlation among these properties makes quality control easier [5]. To design a machine for handling, cleaning, conveying, and storing, the physical, mechanical, and hydraulic properties of agricultural products must be known. Physical characteristics of fruit crops are the most important parameters to determine the proper standards of design of grading, conveying, processing, and packaging systems [6]. Among these physical characteristics, mass, volume, and projected area are the most important ones in determining sizing systems
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