Pipe Flow Velocity Calculator
Find the fluid velocity in a pipe from the flow rate and inner diameter — with optional Reynolds number and laminar/turbulent check.
Method
v = Q / A, A = πD²/4
Re = v·D / ν (ν = kinematic viscosity)
Keep liquid line velocity roughly under 3 m/s to limit erosion and water hammer.
Typical design velocities
| Service | Velocity |
|---|---|
| Pump suction | 0.6–1.5 m/s |
| Pump discharge / liquid lines | 1.5–3 m/s |
| Gas lines | 10–20 m/s |
Frequently Asked Questions
How do I calculate pipe velocity?
Divide the volumetric flow rate by the pipe cross-sectional area: v = Q / (πD²/4).
What is a good pipe velocity?
For liquids, about 1.5–3 m/s; suction lines lower (0.6–1.5 m/s) to protect the pump.
What is the Reynolds number?
A dimensionless ratio that indicates laminar (<2300) versus turbulent (>4000) flow.
Why does velocity matter?
High velocity causes erosion, noise and water hammer; low velocity allows settling of solids.
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