Is this calculation correct?
calculations for air
velocity, diameter information
8 inches in a foot or 16 inches in feet squared or .6666 squared = .4444 inches
12 inches in a foot = 1 feet squared
Volumetric flow rate (cfm) = velocity of the air (fpm)*cross-sectional area of duct (sf)
683 fpm*.4444 sf = flow rate =303.56 cfm