What is the Venturi effect?

The Venturi effect is the reduction in fluid pressure that occurs when a fluid flows through a constricted section of pipe. As the cross-sectional area decreases, fluid velocity increases and static pressure drops, consistent with conservation of energy (Bernoulli's principle) and conservation of mass (continuity equation).

What formulas does this calculator use?

It uses two equations. The continuity equation A₁v₁ = A₂v₂ gives the throat velocity from inlet velocity and the area ratio. Bernoulli's principle then gives the pressure drop: ΔP = ½ρ(v₂² − v₁²). Volumetric flow rate is Q = A₁ × v₁.

What assumptions apply?

The fluid is incompressible, flow is steady and inviscid (no viscous losses), and the pipe is horizontal (no elevation change between inlet and throat). For gases at low Mach numbers and liquids at moderate flow speeds these assumptions hold well.

How is this different from an orifice plate?

Both restrict flow to create a measurable pressure drop, but a Venturi tube gradually converges then diverges, recovering most of the pressure downstream. An orifice plate has a sharp edge causing more permanent pressure loss. Venturi meters are more efficient but larger and more expensive.

What is the discharge coefficient?

Real Venturi meters introduce a discharge coefficient Cd (typically 0.95–0.99) to account for minor viscous losses. This calculator assumes ideal (Cd = 1) flow; multiply the calculated flow rate by your Cd for a real meter.

Venturi Effect Calculator

Name: Venturi Effect Calculator
Availability: InStock
Author: Nham Vu

Enter pipe and throat diameters plus inlet conditions to find throat velocity, pressure drop, and volumetric flow rate in a Venturi tube.

Fluid

Fluid density ρ (kg/m³)

Pipe Geometry

Inlet diameter D₁ (mm)

Throat diameter D₂ (mm)

Constriction ratio β = D₂/D₁ 0.500

Inlet Flow

Inlet velocity v₁ (m/s)

Inlet Pressure (optional)

Used to show absolute throat pressure and check for cavitation risk.

Fill in the inputs and click Calculate.

Throat Velocity

—

m/s

Pressure Drop

—

Flow Rate Q

—

L/s

Throat Pressure

—

Step-by-Step Breakdown

Inlet vs. Throat Comparison

Parameter	Inlet	Throat

Summary

Enter pipe and throat diameters plus inlet conditions to find throat velocity, pressure drop, and volumetric flow rate in a Venturi tube.

How it works

Enter the pipe (inlet) diameter and throat diameter in millimeters.
Select the fluid type or enter a custom density.
Enter the inlet velocity or volumetric flow rate.
Optionally enter the inlet pressure to calculate the absolute throat pressure.
Click Calculate — the tool applies the continuity equation (A₁v₁ = A₂v₂) and Bernoulli's principle (ΔP = ½ρ(v₂² − v₁²)) to compute all outputs.

Use cases

Size a Venturi meter for measuring flow rate in industrial pipelines.
Calculate the pressure drop across a carburetor throat in engine design.
Verify Venturi tube readings in a fluid mechanics lab.
Estimate throat velocity for a nozzle or injector design.
Determine minimum inlet pressure to avoid cavitation at the throat.
Explore the relationship between pipe constriction ratio and pressure drop.

Frequently Asked Questions

Last updated: 2026-07-26 · Reviewed by Nham Vu