Pipe Velocity Calculator
Calculate the flow velocity inside a circular pipe from volumetric flow rate and inner diameter.
How it works
- 1Enter the volumetric flow rate (L/s or gpm) and the pipe inner diameter (mm or in).
- 2The calculator finds the area A = π/4·d², then v = Q ÷ A.
- 3Results show velocity in your chosen units and the cross-section area.
Use cases
- Sizing supply and irrigation pipes to stay within 1–2.5 m/s.
- Checking existing pipework can handle a higher pump output.
- Hydraulic design where velocity drives pressure drop and wear.
Frequently asked questions
What is the recommended water velocity?
For water supply, keep velocity between 1 and 2.5 m/s. Below 1 m/s sediment accumulates; above 2.5 m/s erosion, noise, and water-hammer risk rise.
How is velocity calculated?
v = Q ÷ A, with A = π/4·d² for a circular pipe. 10 L/s through a 100 mm pipe gives A ≈ 0.00785 m², so v ≈ 1.27 m/s.
Inner or outer diameter?
Always the inner (bore) diameter — the clear opening. Using the outer diameter overstates area and understates velocity.
Related tools
See all →Find the gear ratio, output speed, torque, and mechanical advantage of a gear pair, in metric or imperial.
Calculate the overall ratio and output speed of a multi-stage compound gear train.
Calculate shaft torque from power and rotational speed in metric or imperial units.
Calculate the mechanical power transmitted by a rotating shaft from torque and shaft speed.