Abstract: A dynamic-capacity-demand-forecast system in the manufacture of semiconductor integrated circuits includes several steps. N types of products and m types of processing steps are in a processing line. The turn ratio of each products at each stages on a specified working day is calculated and the work-in-process (WIP) of every product at each stages on the same day is determined. According to these two numbers, the WIP on the next working day can be calculated, and then the move on the next working day is determined. Using this formula, the move of each product at each stage in future is obtained. Also, the summation the moves of all products at all stages on a working day are equal to, the capacity demand of the processing line on that day. The quantity of the throughput of the wafers may thus be determined and the supervisor can decide how to vary the parameters of the processing line.