Rectangular Duct Area Calculator
Area and aspect ratio for rectangular duct.
Enter your values
ⓘ Live results
Results
- Area
- 112 sq in
- In sq ft
- 0.7778
- Aspect ratio
- 1.75:1
- Rating
- Good — efficient shape
Quick answer
Rectangular duct area is width times height, and the aspect ratio should ideally stay under 4:1.
A = w x h
How to use the Rectangular Duct Area Calculator
- 1Enter the inside width and height.
- 2Check the aspect ratio stays at or below 4:1.
- 3Convert to an equivalent round diameter for friction charts.
Worked example
Using the values the calculator loads with:
Inputs
- Width14 in
- Height8 in
Results
- Area112 sq in
- In sq ft0.7778
- Aspect ratio1.75:1
- RatingGood — efficient shape
Frequently asked questions
Why does aspect ratio matter?
Flat ducts have more wall per unit of area, so friction and material cost both rise.
Best shape?
Round moves the most air for the least friction and sheet metal.
About this calculator
- Built and reviewed by James Whitfield · How we build and test calculators
- Report an error
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.