Air Velocity Calculator
Duct air speed in FPM, m/s and mph.
Enter your values
ⓘ Live results
Results
- Velocity
- 1,091 FPM
- In m/s
- 5.54
- In mph
- 12.4
- In km/h
- 19.95
Quick answer
Air velocity is the volumetric flow rate divided by the cross-sectional area of the duct.
v = Q / A
How to use the Air Velocity Calculator
- 1Enter the airflow in CFM.
- 2Enter the duct's free cross-sectional area in square feet.
- 3Compare against the target velocity for that duct type.
Worked example
Using the values the calculator loads with:
Inputs
- Airflow600 CFM
- Duct area0.55 sq ft
Results
- Velocity1,091 FPM
- In m/s5.54
- In mph12.4
- In km/h19.95
Frequently asked questions
What velocity suits a main trunk?
Residential trunks usually run 700–900 FPM; commercial mains often 1200–1800 FPM.
What about return air?
Keep returns slower — around 500–700 FPM — because return grilles transmit noise easily.
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.