Technical Abstract: Characterizing tomato geometries with different shapes and sizes would facilitate the design of tomato processing equipments and promote computer-based engineering simulations. This research sought to develop a three-dimensional geometric model that can describe the morphological attributes of processing-tomatoes different with mass. A new tomato shape equation was derived as a radius function under polar coordinates systems, which defines a representation of processing-tomato fruit in terms of the dimensional parameters and shape coefficients. To determine the unknown coefficients in the tomato shape equation, the analytical relationships of tomato shape and size were first deduced based on the morphometric attributes of processing-tomatoes and were then correlated to the distribution of tomato mass using linear regression analysis. Geometric model of process-tomatoes was generated in three- and two-dimensional forms and enable displays of size and shape variance with mass. Validations of the established three-dimensional model with experimentally measured tomato mass and surface area resulted in good consistency and accuracy. The developed model can characterize a number of tomato geometric attributes, such as volume, surface area, and radius of curvature, etc. By converting to a finite element mesh representation, the geometric model demonstrated a good potential for its application in numerical simulation studies. The proposed new approach to capture important shape features of tomatoes with simple measurement proved to be a practical and effective tool for tomato-related engineering applications.