Duct Transition Calculator

Inputs

View results
Design airflow through the transition.
cfm
Rectangular inlet duct width.
in
Rectangular inlet duct height.
in
Rectangular outlet duct width.
in
Rectangular outlet duct height.
in
Straight centerline length of the reducer or transition.
in
Allowed side taper angle used to recommend minimum transition length.
°
Added sheet width along one longitudinal seam for blank-area estimating.
in
Sheet-metal thickness for the approximate shell mass.
in
Sheet material density for approximate transition mass.
lb/ft³
Air density used for velocity pressure.
lb/ft³

Results

Default result
Edit inputs
Recommended length(Lrec)
7.347in
Pass

minimum length for the entered 15 deg taper limit

Also computed

Length margin(Lmargin)Pass12.34in

entered transition is at or above the taper-length screen

Controlling taper angle(theta)Pass5.711°

larger of width taper and height taper

Inlet velocity(v1)Pass689ft/min

typical comfort-duct screening range

Outlet velocity(v2)Pass1,148ft/min

typical comfort-duct screening range

Area ratio(Aratio)Caution1.667

larger opening area divided by smaller opening area

Velocity pressure change(dPv)0.05246in. w.g.

positive means the outlet velocity pressure is higher than the inlet

Duct transition length and velocity previewDuct transition previewTop and side profiles show the controlling taper angle for the entered length.Top width taperSide height taperRecommended length: 7.35 inControlling angle: 5.7 degOutlet velocity: 5.83 m/s
Method notes 3 notes
  • Recommended length uses L >= max(|W1-W2|/2, |H1-H2|/2) / tan(theta_max).
  • For a round outlet, the layout screen compares the round diameter against the rectangular inlet width and height; it is not a triangulated square-to-round pattern.
  • Velocity pressure change is only the change in dynamic pressure. Add transition fitting losses separately in the static-pressure budget.

Powered by MachineCalcs ↗