Pipe Velocity and Diameter Calculator

Calculate average pipe flow velocity from volumetric flow rate and pipe inner diameter, or estimate the required pipe inner diameter from flow rate and target velocity.

Inputs are converted to SI units before calculation: flow rate to m3/s, velocity to m/s, and pipe inner diameter to m.

Input Method Selection

Input Form

Item Value Unit
Volumetric flow rate Q
Pipe inner diameter D
Target velocity u

Calculation Result

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Formula Used

A = pi D^2 / 4, u = Q / A, or D = sqrt(4 Q / (pi u))

  • Q: volumetric flow rate [m3/s]
  • A: pipe cross-sectional area [m2]
  • u: average pipe flow velocity [m/s]
  • D: pipe inner diameter [m]

Input Values Converted to SI Units

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Caution Note

This is a simplified calculation based on average velocity in a circular pipe. For actual pipe design, also check Reynolds number, pressure drop, pipe roughness, allowable velocity, erosion, noise, and available standard pipe sizes.

When the flow rate is 0, velocity mode returns a velocity of 0, and diameter mode returns a required inner diameter of 0.

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