Rectangular Duct Area Calculator
Area and aspect ratio for rectangular duct.
Enter your values
Enter the width in in.
Enter the height in in.
Results update instantly as you type — no submit needed. Your values are remembered on this device, and the shareable link reopens the calculator with exactly these numbers.
- 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
At a glance
| What it does | Area and aspect ratio for rectangular duct. |
|---|---|
| Category | HVAC & Airflow |
| Inputs needed | Width, Height |
| Main output | Area |
| Formula | A = w x h |
| Cost | Free — no sign-up, no download |
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.
Inputs explained
- Width(in)
- Enter the width in in.
- Height(in)
- Enter the height in in.
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.
What do I need to enter into the Rectangular Duct Area Calculator?
Just 2 values: width, height. Every field starts with a realistic example, so you can change one number at a time and watch the result update instantly.
How does the Rectangular Duct Area Calculator work out the answer?
Rectangular duct area is width times height, and the aspect ratio should ideally stay under 4:1. It applies the formula A = w x h and shows the working so you can check each step by hand.
Is the Rectangular Duct Area Calculator free, and do I need an account?
It is completely free with no sign-up, no download and no usage limit. Everything is calculated in your browser, so the numbers you type never leave your device.
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.