This paper describes an algorithm designed to estimate the future cell throughput of a multi-rate wireless network based on measurements. The achievable throughput of a cell depends on the transmission rate used by the mobile nodes. We propose to use a measurement window to gauge the aggregate channel usage by multiple nodes over a period of time instead of predicting the movement and the rate of each node. It is found that the statistics of the average channel occupation time per frame follow the normal distribution. This offers a high degree of confidence in the prediction of cell throughput.