Venturi Flow Calculator
Airflow from a venturi meter's throat differential pressure.
Enter your values
ⓘ Live results
Results
- Airflow
- 252 CFM
- Throat velocity
- 21.4 ft/s
- Beta ratio
- 0.6
Quick answer
Venturi flow is found from the throat area, the discharge coefficient, the beta ratio velocity correction and the square root of differential pressure.
Q = Cd x A2 / sqrt(1 - beta^4) x sqrt(2 x dP / rho)
How to use the Venturi Flow Calculator
- 1Enter the inlet and throat diameters of the venturi, the differential pressure and air density.
- 2The tool applies the beta-ratio correction for the velocity of approach.
- 3Use the manufacturer's calibrated discharge coefficient when available for best accuracy.
Worked example
Using the values the calculator loads with:
Inputs
- Inlet pipe diameter10 in
- Throat diameter6 in
- Differential pressure3.0 in wc
- Discharge coefficient0.98
- Air density0.075 lb/ft3
Results
- Airflow252 CFM
- Throat velocity21.4 ft/s
- Beta ratio0.6
Frequently asked questions
Why correct for beta ratio?
The upstream velocity is not negligible, so the simple orifice equation must be corrected for the area contraction ratio.
Venturi vs orifice plate?
Venturis have much lower permanent pressure loss and a higher discharge coefficient close to 1.
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.