A method and apparatus calculates production quantities of a production system such as the throughput of a tool group, good unit equivalents of a tool group, number of units shipped and started for each step of the production system, process time of each step, average processing time, rate and units processed for each tool group, number of tools required and minimum and actual number of test cells or tool groups required. Some or all of these production quantities are calculated by taking into account the downtime of any controller of a tool group.