Pipe Velocity and Diameter Calculator

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

STEP 1

Enter Flow Conditions

Select whether to calculate velocity or diameter, then enter flow rate and the required pipe value.

Calculation mode

Required for velocity calculation.

Required for diameter calculation.

Calculation Result

Enter flow conditions and press Calculate to see the result.

Formula and Notes

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]

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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