Properly constructed cotton modules can prevent reduced lint value and increased ginning costs after significant rainfall occurs. Modules should be constructed with a convex top surface so that water will not collect on the module cover. Many modules are constructed with undesirable shapes because operators are inexperienced, must quickly construct modules, and have difficulty estimating the mass of cotton at various locations in the module. The objectives of this research were to design a system that would provide the operator an image of the predicted module shape, evaluate the accuracy of the system in predicting module shape, and determine the usefulness of this system. Final module shape was predicted by determining the height of the compressed cotton along the length of the module and this shape was graphically displayed for the operator. The display assisted the operator in moving cotton to appropriate locations for creation of desirably shaped modules. The heights of modules constructed with and without the feedback system were measured. The system correctly predicted the height with 67% accuracy. Use of the feedback system resulted in a 55% reduction in water collection area on the top surface of modules. Module builder operators indicated that the system was useful. The module builder feedback system is a simple and inexpensive tool that has the potential to provide rapid payback for producers.