Belt Conveyors for Bulk Materials Calculations by CEMA 5 . Belt Conveyor Capacity Table 1. Determine the surcharge angle of the material. The surcharge angle, on the average, will be 5 degrees to 15 degrees less than the angle of repose. (ex. 27° 12° = 15°) 2. Determine the density of the material in pounds per cubic foot (lb/ft3). 3.