Dust Collection CFM Calculator
Workshop dust collector sizing by machine.
Enter your values
Enter the largest machine requirement in CFM.
Enter the second machine (if run together) in CFM.
Enter the main duct diameter in in.
Enter the duct leakage allowance 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.
- Collector size needed
- 700 CFM
- Duct velocity
- 4,840 FPM
- Transport verdict
- Higher than needed — upsize duct to cut static
- Duct area
- 0.136 sq ft
- Ideal duct diameter
- 5.5 in
Quick answer
Each machine has a port CFM requirement, and duct velocity must stay above 3,500–4,000 FPM to keep chips moving.
CFM = sum of active machine requirements; velocity = CFM / duct area
At a glance
| What it does | Workshop dust collector sizing by machine. |
|---|---|
| Category | HVAC & Airflow |
| Inputs needed | Largest machine requirement, Second machine (if run together), Main duct diameter, Duct leakage allowance |
| Main output | Collector size needed |
| Formula | CFM = sum of active machine requirements; velocity = CFM / duct area |
| Cost | Free — no sign-up, no download |
How to use the Dust Collection CFM Calculator
- 1Enter the CFM demand of the biggest machine you run.
- 2Add a second machine only if you genuinely run two at once.
- 3Check that duct velocity stays between 3,500 and 4,500 FPM.
Inputs explained
- Largest machine requirement(CFM)
- Enter the largest machine requirement in CFM.
- Second machine (if run together)(CFM)
- Enter the second machine (if run together) in CFM.
- Main duct diameter(in)
- Enter the main duct diameter in in.
- Duct leakage allowance(%)
- Enter the duct leakage allowance in %.
Worked example
Using the values the calculator loads with:
Inputs
- Largest machine requirement600 CFM
- Second machine (if run together)0 CFM
- Main duct diameter5 in
- Duct leakage allowance10 %
Results
- Collector size needed700 CFM
- Duct velocity4,840 FPM
- Transport verdictHigher than needed — upsize duct to cut static
- Duct area0.136 sq ft
- Ideal duct diameter5.5 in
Frequently asked questions
Why is velocity so critical?
Below about 3,500 FPM heavy chips drop out of the airstream and block the duct.
Is a shop vac enough?
A shop vac gives high suction but only 60–150 CFM — fine for sanders, useless for a table saw.
What do I need to enter into the Dust Collection CFM Calculator?
Just 4 values: largest machine requirement, second machine (if run together), main duct diameter, duct leakage allowance. 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 Collection CFM Calculator work out the answer?
Each machine has a port CFM requirement, and duct velocity must stay above 3,500–4,000 FPM to keep chips moving. It applies the formula CFM = sum of active machine requirements; velocity = CFM / duct area and shows the working so you can check each step by hand.
Is the Dust Collection CFM 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.