Air Duct Flow calculator

SI Units

air velocity (m/s)
diameter (m)

or alternatively

side length - a (m)
side length - b (m)

Imperial Units

air velocity (ft/min)
diameter (in)

or alternatively

side length - a (in)
side length - b (in)

Air flow in air ducts formula

vi = qi / Ai = 576 qi / (π di2) = 144 qi / (ai bi)

where, qi = air flow (cfm), vi = air velocity (ft/min), di = diameter of duct (inches), Ai = area of duct (square feet), bi = width of duct (inches), ai = width of duct (inches)