Capacity ($C$):

$$C = \frac{(D^2 - d^2) \cdot P \cdot N}{36.6}$$

Where:

• $C$ is the capacity of the screw conveyor, in cubic feet per hour (ft³/hr).
• $D$ is the screw diameter, in inches (in).
• $d$ is the shaft diameter, in inches (in).
• $P$ is the screw pitch, in inches (in), normally equal to $D$.
• $N$ is the shaft speed, in revolutions per minute (rpm).