This paper is concerned with prediction of machine utilization and specific work-batch completions in a manufacturing workshop which employs dispatching rules for work loading. Predictions from a simple iterative computer simulation are compared with those from a real-time manual simulation. The computer simulation is varied by adjusting the number of iterations and the allocated process capacities, and conclusions are drawn on the best method of achieving improvement in the fit of the model. The technique is applied on a microcomputer, but it can be implemented on a mini or mainframe if manufacturing information data flies currently exist. It will be of value in short term allocation of flexible resources, in supplying detailed predictions of individual work batch completions to improve service levels or in short term planning of maintenance to coincide with machine idle periods.