Pipe Flow Velocity Calculator
Flow velocity inside a pipe from the flow rate and the internal diameter.
Results
Speed
1.4147
m/s
Area
19.635
cm²
Flow rate
166.67
L/min
What this tool does
Velocity is the flow rate divided by the cross-sectional area, and it is the number that decides whether a pipe is noisy, erosive or simply undersized. Water systems are usually designed for roughly 1–2 m/s; use the internal diameter, not the nominal size.
Formula
v = Q ÷ A , A = π × d² ÷ 4
Variables
| Symbol | Meaning | Unit |
|---|---|---|
q | Flow rate | m³/h |
d | Diameter | mm |
V | Speed | m/s |
A | Area | cm² |
QL | Flow rate | L/min |
Worked example
- Flow rate10 m³/h
- Diameter50 mm
- Speed1.4147 m/s
- Area19.635 cm²
- Flow rate166.67 L/min
Limitations
- The formula assumes ideal conditions: no friction losses, no air resistance and no efficiency losses unless you enter them.
- For work that must comply with a standard or be signed off, check the result against the applicable code and have it reviewed by a qualified engineer.