Pipe Flow Calculator
Calculate volumetric flow through a full-bore circular pipe from its diameter and flow velocity.
How it works
- 1Enter the pipe inner diameter and the mean flow velocity in your chosen units.
- 2The calculator finds the area A = π/4·d², then applies Q = A·v.
- 3Results show m³/h or cfm, L/s or gpm, m³/s, and litres per minute.
Use cases
- Sizing water mains and distribution pipes in building services and HVAC.
- Verifying a pump can pass the required flow without excessive velocity.
- Cross-checking flow-meter readings against theoretical capacity.
Frequently asked questions
What formula does this use?
Q = (π/4·d²)·v. A 150 mm pipe at 1.5 m/s gives Q ≈ 0.0265 m³/s ≈ 95.4 m³/h.
Does it include friction losses?
No — it assumes a uniform mean velocity across the full bore. For pressure drop, use the Darcy–Weisbach head-loss calculator.
What is a safe water velocity?
Roughly 0.5–1.5 m/s for distribution and up to 3 m/s for short high-pressure runs. Above 3 m/s risks erosion, noise, and water hammer.
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