Pipe Velocity Calculator
Flow velocity and pipe sizing.
Enter your values
Enter the flow rate in L/s.
Enter the internal diameter in mm.
Enter the max recommended velocity in m/s.
Results update instantly as you type — no submit needed. Your values are remembered on this device, and the shareable link reopens the calculator with exactly these numbers.
- Velocity
- 1.59 m/s
- Cross-sectional area
- 50.27 cm²
- Within limit?
- Yes
- Min diameter for limit
- 64 mm
Quick answer
Pipe velocity is flow rate divided by internal cross-sectional area.
v = Q ÷ A
At a glance
| What it does | Flow velocity and pipe sizing. |
|---|---|
| Category | Engineering |
| Inputs needed | Flow rate, Internal diameter, Max recommended velocity |
| Main output | Velocity |
| Formula | v = Q ÷ A |
| Cost | Free — no sign-up, no download |
How to use the Pipe Velocity Calculator
- 1Enter the design flow rate.
- 2Enter internal pipe diameter.
- 3Compare velocity against the recommended maximum.
Inputs explained
- Flow rate(L/s)
- Enter the flow rate in L/s.
- Internal diameter(mm)
- Enter the internal diameter in mm.
- Max recommended velocity(m/s)
- Enter the max recommended velocity in m/s.
Worked example
Using the values the calculator loads with:
Inputs
- Flow rate8 L/s
- Internal diameter80 mm
- Max recommended velocity2.5 m/s
Results
- Velocity1.59 m/s
- Cross-sectional area50.27 cm²
- Within limit?Yes
- Min diameter for limit64 mm
Frequently asked questions
What velocity is too high?
Above 2.5 m/s in water pipes causes noise and erosion.
Why does velocity matter?
Friction losses rise with the square of velocity.
What do I need to enter into the Pipe Velocity Calculator?
Just 3 values: flow rate, internal diameter, max recommended velocity. Every field starts with a realistic example, so you can change one number at a time and watch the result update instantly.
How does the Pipe Velocity Calculator work out the answer?
Pipe velocity is flow rate divided by internal cross-sectional area. It applies the formula v = Q ÷ A and shows the working so you can check each step by hand.
Is the Pipe Velocity Calculator free, and do I need an account?
It is completely free with no sign-up, no download and no usage limit. Everything is calculated in your browser, so the numbers you type never leave your device.
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.