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Fluid Mechanics Calculators

Fluid Velocity Calculator

Fluid velocity in a pipe from flow rate and diameter, with the continuity equation for size changes.

Also known as pipe velocity, water velocity, continuity equation.

Enter values

Results update as you type.

Result

Velocity

0.849 m/s

Pipe area
1,963.5 mm²
Velocity (ft/s)
2.78
Velocity in 25 mm pipe
3.395 m/s

About the Fluid Velocity Calculator

Fluid velocity in a pipe from flow rate and diameter, with the continuity equation for size changes.

Also known as: pipe velocity, water velocity, continuity equation.

How to use this calculator

  1. Enter flow rate, pipe inside diameter, second pipe diameter (optional).
  2. The result updates instantly as you type — press Calculate (or Enter) at any time.
  3. Review the breakdown shown under the main result.
  4. Use Copy result or Share to save the answer or send a link with your inputs.

Fluid Velocity formula

v = Q / A · A₁v₁ = A₂v₂

Worked example

Using the values pre-filled in the calculator above:

  • Flow rate = 100 L/min
  • Pipe inside diameter = 50 mm
  • Second pipe diameter (optional) = 25 mm

the calculator returns:

  • Velocity: 0.849 m/s
  • Pipe area: 1,963.5 mm²
  • Velocity (ft/s): 2.78
  • Velocity in 25 mm pipe: 3.395 m/s