Fan Inlet Velocity Calculator
Air velocity entering a fan's inlet cone or box.
Enter your values
ⓘ Live results
Results
- Inlet velocity
- 4,584 FPM
- Inlet area
- 2.182 sq ft
- Rating
- High - check for noise and efficiency loss
Quick answer
Fan inlet velocity equals CFM divided by the inlet's free area.
V = CFM / Area
How to use the Fan Inlet Velocity Calculator
- 1Enter the fan's design CFM and the diameter of the inlet cone or duct connection.
- 2Read the resulting inlet velocity.
- 3Keep inlet velocity moderate (often under ~2,500-3,000 FPM) to minimize noise and turbulence losses.
Worked example
Using the values the calculator loads with:
Inputs
- Fan airflow10000 CFM
- Inlet diameter20 in
Results
- Inlet velocity4,584 FPM
- Inlet area2.182 sq ft
- RatingHigh - check for noise and efficiency loss
Frequently asked questions
Why does high inlet velocity hurt performance?
Turbulent, uneven inlet flow (system effect) reduces the fan's effective pressure and increases noise, sometimes significantly.
What about outlet velocity?
Outlet (discharge) velocity should also be checked separately against duct connection guidelines.
About this calculator
- Built and reviewed by James Whitfield · How we build and test calculators
- Report an error
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.