Propeller Fan CFM Calculator
Free-air CFM of a propeller (axial) fan from disk area and velocity.
Enter your values
Enter the blade diameter in in.
Enter the average discharge 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.
- Free-air CFM
- 3,770 CFM
- Swept area
- 3.14 sq ft
- Note
- Free-air estimate — CFM drops quickly against added static pressure
Quick answer
Propeller fan CFM equals the fan's swept disk area multiplied by the average discharge air velocity.
CFM = Area x V
At a glance
| What it does | Free-air CFM of a propeller (axial) fan from disk area and velocity. |
|---|---|
| Category | HVAC & Airflow |
| Inputs needed | Blade diameter, Average discharge velocity |
| Main output | Free-air CFM |
| Formula | CFM = Area x V |
| Cost | Free — no sign-up, no download |
How to use the Propeller Fan CFM Calculator
- 1Enter the propeller fan's blade tip diameter and its measured or rated discharge velocity.
- 2Read the estimated free-air CFM (no ductwork resistance).
- 3Remember propeller fans lose CFM fast once any static pressure is added — check the manufacturer's curve for ducted applications.
Inputs explained
- Blade diameter(in)
- Enter the blade diameter in in.
- Average discharge velocity(FPM)
- Enter the average discharge velocity in FPM.
Worked example
Using the values the calculator loads with:
Inputs
- Blade diameter24 in
- Average discharge velocity1200 FPM
Results
- Free-air CFM3,770 CFM
- Swept area3.14 sq ft
- NoteFree-air estimate — CFM drops quickly against added static pressure
Frequently asked questions
Can propeller fans handle ductwork?
Only very short, low-resistance duct runs — for real ductwork, use a vane-axial or centrifugal fan instead.
Where are propeller fans used?
Wall or roof exhaust with no ductwork, or condenser/cooling tower fans discharging to open air.
What do I need to enter into the Propeller Fan CFM Calculator?
Just 2 values: blade diameter, average discharge 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 Propeller Fan CFM Calculator work out the answer?
Propeller fan CFM equals the fan's swept disk area multiplied by the average discharge air velocity. It applies the formula CFM = Area x V and shows the working so you can check each step by hand.
Is the Propeller Fan 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.