In this paper, a low cost sensor system has been designed to automatically compute the volume and surface area of axi-symmetric agricultural products such as eggs, lemons, limes and tamarillos. This sensor system is based on a low-cost image sensor and a low-cost programmable microcontroller. We have demonstrated that an unsupervised image-processing algorithm can generate reliable results by capturing just one image of the axi-symmetric object from a fixed projection. The volume and surface area are computed by approximating the object as a sum of elementary right conical frustums. The analytical and experimental results suggest that this automated sensor system is potentially a good alternative to manual measurements for axi-symmetric agricultural products, with an overall cost of under US$50. (c) 2006 Elsevier Ltd. All rights reserved.