The ability to accurately estimate grip force requirements may be important in exposure assessment, determining fitness for duty, or setting rehabilitation goals. This study investigates the effects of learning and experience, measurement system, and the nature of the task on grip force estimate accuracy. The grip forces applied during "pure" power grip tasks and simulated meat cutting tasks conducted in the laboratory, and during meat cutting operations at meat packing plants were measured with an instrumented tool handle. Estimates were recorded using the tool handle and a modified hand dynamometer. The results indicate that estimate accuracy varied greatly from individual to individual. No significant effect of learning on estimate accuracy was observed. The result of the meat cutting simulation and field study suggest that the force distribution at the hand-tool interface can markedly affect estimates. Great care must be taken in the collection of grip force estimates, as well as in the interpretation of the data. Improved understanding of the factors affecting estimates of grip force requirements should aid in the interpretation of functional capacity evaluations, and in the establishment of goals for rehabilitation.