Optimum truck numbers of an enterprise can be found by dividing the period of time passed between a departing truck after loading, the arrival at the dumping location, the arrival at the point of loading again and the average loading time parameters of a truck. The average loading time of the truck is directly associated with the bucket fill factor and cycle time of the excavator. While the bucket fill factor depends on the mechanical strength and the discontinuity characteristics of the rock, the cycle time is related to bucket volume, the strength and the discontinuity characteristics of the rock. in this study, two relations predicting the average cycle time of the bucket fill factor for both hydraulic and electric excavators is done by seven excavators with different bucket volumes. and mass characteristics of eight different rocks from a coal open pit mine. According to the above, the optimum truck number was developed.