Venturi tube is used as flow meter in piping system and where Venturi effect is required. Due to the change in diameter from the inlet to the throat mean velocity is changing while mass flow rate remains constant.

As total pressure remains mainly constant, part of static pressure is transformed into dynamic pressure from the inlet to the throat of tube and pressure drop is created. This is called Venturi effect. Measuring static pressure on the inlet and on the throat - pressure drop, with this calculator, flow rate can be calculated, based on the energy conservation law and Bernoulli theorem.

- Flow rate for known Venturi size and pressure difference
- Flow velocity in the Venturi inlet
- Discharge coefficient calculation
- Gas expansion coefficient for compressible flow

In Selection section you can select values to input. Not selected values will be calculated. You select between:

- flowing fluid - gas or liquid
- pressure after the Venturi tube or pressure difference at inlet and throat of Venturi tube
- Venturi inlet and throat diameter
- density or temperature for gases
- kinematic or dynamic viscosity
- Venturi tube manufacturing type
- calculation within or out of ISO5167 constraints
- calculation of discharge coefficient or manual input

In Report section you have instant calculation report for input values. From there you can copy/paste report to your text editor.

- Conversion between volumetric and mass flow rate
- Calculation of Reynolds number included
- Applicable for non-compressible liquids and compressible perfect gases
- For three different kind of Venturi tubes - machined, welded and casted
- For single-phase fluid, subsonic, non-pulsating flow
- Pressure ratio p
_{2}/p_{1}must be equal or greater than 0.75 - ISO 5167 based calculation

- q - volumetric flow rate
- Fluid flow rate in terms of units of volume per unit of time
- ṁ - mass flow rate
- Fluid flow rate in terms of units of mass per unit of time
- D
_{1}- inlet diameter of Venturi tube - Internal inlet Venturi tube diameter
- D
_{2}- Venturi tube throat diameter - Diameter of Venturi tube throat where maximum flow velocity and minimum pressure is created
- V
_{1}- inlet velocity - Flow velocity at inlet part of Venturi tube where flow diameter is D
_{1} - A - area
- Internal pipe cross section area
- ρ - fluid inlet density
- Density of fluid at inlet part of Venturi tube in terms of mass per unit of volume
- ν - kinematic viscosity
- Result of fluid particles colliding to each other and moving at different velocities in terms of area per square unit of time
- μ - dynamic viscosity
- Result of fluid particles colliding to each other and moving at different velocities in terms of mass per square unit of distance and time
- κ- isentropic coefficient
- Specific heat ratio
- e - expansion factor
- Coefficient used for compressible flow calculation
- C - coefficient of discharge
- Coefficient used for Venturi tube, based on the ISO 5167
- R
_{eD}- inlet Reynolds number - Reynolds number calculated in inlet of Venturi tube
- p
_{1}- pressure on the inlet - Absolute inlet pressure in the Venturi tube
- p
_{2}- pressure on the outlet - Absolute pressure in the Venturi throat - minimal pressure created by increase of velocity in the Venturi tube throat
- p
_{1}- p_{2}- pressure drop - Pressure difference between inlet and throat of Venturi tube
- T - temperature
- Fluid temperature for gas density calculation based on the ideal gas state equation
- R - gas constant
- Gas constant in terms of energy per unit of mass and temperature, for gas density calculation using ideal gas state equation

- Related links:
- Venturi effect on Wikipedia
- Giovanni Battista Venturi
- ISO 5167-4