Dust Collector Main Duct Calculator
Main trunk sizing for a shared dust collection system.
Enter your values
Enter the machine 1 cfm in CFM.
Enter the machine 2 cfm in CFM.
Enter the machines run simultaneously you are working with.
Enter the transport velocity in FPM.
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.
- Main duct design CFM
- 600 CFM
- Main duct diameter
- 5.2 in
- Collector sizing
- Select a collector rated for at least 690 CFM at expected static
- Note
- Static pressure adds up through the longest branch run — verify with the collector's fan curve
Quick answer
The main trunk duct should be sized for the largest simultaneous CFM demand (usually the biggest single machine, or two if run together) at 3500-4500 FPM.
Main CFM = max simultaneous branch demand; diameter from CFM and velocity
At a glance
| What it does | Main trunk sizing for a shared dust collection system. |
|---|---|
| Category | HVAC & Airflow |
| Inputs needed | Machine 1 CFM, Machine 2 CFM, Machines run simultaneously, Transport velocity |
| Main output | Main duct design CFM |
| Formula | Main CFM = max simultaneous branch demand; diameter from CFM and velocity |
| Cost | Free — no sign-up, no download |
How to use the Dust Collector Main Duct Calculator
- 1List the CFM requirement of each machine on the system.
- 2Decide how many run simultaneously in practice.
- 3Size the main trunk for the simultaneous total, and pick a collector rated above that with margin.
Inputs explained
- Machine 1 CFM(CFM)
- Enter the machine 1 cfm in CFM.
- Machine 2 CFM(CFM)
- Enter the machine 2 cfm in CFM.
- Machines run simultaneously
- Enter the machines run simultaneously you are working with.
- Transport velocity(FPM)
- Enter the transport velocity in FPM.
Worked example
Using the values the calculator loads with:
Inputs
- Machine 1 CFM600 CFM
- Machine 2 CFM400 CFM
- Machines run simultaneously1
- Transport velocity4000 FPM
Results
- Main duct design CFM600 CFM
- Main duct diameter5.2 in
- Collector sizingSelect a collector rated for at least 690 CFM at expected static
- NoteStatic pressure adds up through the longest branch run — verify with the collector's fan curve
Frequently asked questions
Do I size for every machine running at once?
Rarely necessary in a small shop — size for the realistic worst case, usually 1-2 machines running together.
What if my collector is undersized?
Airflow and static pressure both suffer, leading to poor capture and duct clogging at the far end of the system.
What do I need to enter into the Dust Collector Main Duct Calculator?
Just 4 values: machine 1 cfm, machine 2 cfm, machines run simultaneously, transport velocity. 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 Dust Collector Main Duct Calculator work out the answer?
The main trunk duct should be sized for the largest simultaneous CFM demand (usually the biggest single machine, or two if run together) at 3500-4500 FPM. It applies the formula Main CFM = max simultaneous branch demand; diameter from CFM and velocity and shows the working so you can check each step by hand.
Is the Dust Collector Main Duct 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.