Duct Traverse Points Calculator
Number of equal-area traverse points for a round or rectangular duct.
Enter your values
Choose one of: Round, Rectangular.
Enter the diameter or larger side 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.
- Recommended traverse points
- 16
- Layout
- Concentric equal-area rings, 4+ radii
- Minimum straight duct upstream
- 7.5 diameters (or equivalent)
Quick answer
Larger ducts need more equal-area traverse points to get an accurate average velocity; small ducts need fewer.
Points scale with duct diameter/side length per ASHRAE/AABC traverse guidance
At a glance
| What it does | Number of equal-area traverse points for a round or rectangular duct. |
|---|---|
| Category | HVAC & Airflow |
| Inputs needed | Duct shape, Diameter or larger side |
| Main output | Recommended traverse points |
| Formula | Points scale with duct diameter/side length per ASHRAE/AABC traverse guidance |
| Cost | Free — no sign-up, no download |
How to use the Duct Traverse Points Calculator
- 1Select round or rectangular duct and enter its diameter or largest side dimension.
- 2Read the recommended number of equal-area traverse points.
- 3Locate the traverse plane at least 7.5 duct diameters downstream of a disturbance where possible.
Inputs explained
- Duct shape
- Choose one of: Round, Rectangular.
- Diameter or larger side(in)
- Enter the diameter or larger side in in.
Worked example
Using the values the calculator loads with:
Inputs
- Duct shapeRound
- Diameter or larger side18 in
Results
- Recommended traverse points16
- LayoutConcentric equal-area rings, 4+ radii
- Minimum straight duct upstream7.5 diameters (or equivalent)
Frequently asked questions
What if I can't get straight duct length?
Use more points and expect greater uncertainty; note the limitation in the TAB report.
Log-Tchebycheff vs equal-area?
Both are accepted; equal-area is simpler to lay out and commonly used in the field.
What do I need to enter into the Duct Traverse Points Calculator?
Just 2 values: duct shape, diameter or larger side. 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 Duct Traverse Points Calculator work out the answer?
Larger ducts need more equal-area traverse points to get an accurate average velocity; small ducts need fewer. It applies the formula Points scale with duct diameter/side length per ASHRAE/AABC traverse guidance and shows the working so you can check each step by hand.
Is the Duct Traverse Points 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.