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Fluid Flow Rate Calculator

Find the volumetric flow rate through a pipe from cross-sectional area and velocity.

Inputs

Saved Scenarios

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Flow Rate (L/s)

20.00

Flow Rate (m³/s)

0.02000

Spark says

How it's calculated

Formula

Q=A×VQ = A \times V
A
— Pipe or channel cross-sectional area
V
— Average fluid velocity

What is the Fluid Flow Rate Calculator?

The continuity equation for incompressible flow states that volumetric flow rate equals cross-sectional area times average velocity — one of the most fundamental relationships in fluid mechanics and pipe sizing.

How to use it

  1. 1 Enter the pipe or channel's cross-sectional area (for a circular pipe, area = π × radius²).
  2. 2 Enter the average fluid velocity.

Worked examples

0.01 m² area, 2 m/s velocity

About 20 liters per second.

Try it

Limitations

  • •Assumes incompressible flow and a uniform velocity profile across the cross-section — real flows have velocity gradients (faster in the center, slower near walls).

Frequently asked questions

Why does flow speed up in a narrower pipe?

Since Q = A × V must stay constant along a pipe with no branches, a smaller cross-sectional area forces velocity to increase to maintain the same flow rate.