Venturi Meter Calculator Formula
Understand the math behind the venturi meter calculator. Each variable explained with a worked example.
Formulas Used
Velocity at Wide Section
v1 = sqrt(2 * pressure_diff / (density * (pow(area_wide / area_narrow, 2) - 1)))Volume Flow Rate
flow_rate = area_wide * sqrt(2 * pressure_diff / (density * (pow(area_wide / area_narrow, 2) - 1)))Variables
| Variable | Description | Default |
|---|---|---|
pressure_diff | Pressure Difference(Pa) | 5000 |
density | Fluid Density(kg/m3) | 1000 |
area_wide | Wide Section Area (A1)(m2) | 0.01 |
area_narrow | Narrow Section Area (A2)(m2) | 0.005 |
How It Works
Venturi Meter
A Venturi meter measures flow rate by measuring the pressure drop in a constriction.
Formula
From Bernoulli + continuity (A1 v1 = A2 v2):
v1 = sqrt(2 dP / (rho ((A1/A2)^2 - 1)))
The flow rate is Q = A1 * v1.
Worked Example
Water, A1 = 0.01 m2, A2 = 0.005 m2, dP = 5000 Pa.
- 01(A1/A2)^2 = (0.01/0.005)^2 = 4
- 02v1 = sqrt(2 * 5000 / (1000 * 3))
- 03v1 = sqrt(10000 / 3000)
- 04v1 = sqrt(3.333) = 1.826 m/s
- 05Q = 0.01 * 1.826 = 0.01826 m3/s
Frequently Asked Questions
Why is a Venturi meter preferred over an orifice plate?
A Venturi has lower permanent pressure loss because the gradual expansion recovers most of the pressure. Orifice plates are cheaper but waste more energy.
Does a Venturi meter need calibration?
A discharge coefficient (typically 0.98 for well-made Venturis) corrects for small viscous and geometry effects. In theory it can be calculated from first principles.
What fluids can be measured?
Any incompressible fluid: water, oil, chemicals. For gases at low Mach numbers, it also works with a compressibility correction.
Ready to run the numbers?
Open Venturi Meter Calculator