Hidroteknik Calculators
Pipe Diameter & Flow Velocity Calculation
The right pipe diameter keeps flow velocity within the recommended range. Too high causes pressure loss and heating; too low means unnecessary cost.
⚙ Open the Hydraulic Calculator →Formula
Flow velocity
v = Q / (A × 60000)
Q: L/min, A: m², v: m/s
Required inner diameter
D = √(4 × A / π) × 1000
A = Q / (v × 60000) [m²], D: mm
Recommended velocities
Suction: 0.5–1.5 · Pressure: 3–6 · Return: 2–4 m/s
Units
| Quantity | Symbol | Unit |
|---|---|---|
| Flow | Q | L/min |
| Velocity | v | m/s |
| Area | A | m² (×10⁶ → mm²) |
| Inner diameter | D | mm |
Worked Example
Given: Flow Q = 40 L/min, target velocity v = 4 m/s (pressure line).
1) Area: A = 40 / (4 × 60000) = 1.667×10⁻⁴ m² = 166.7 mm²
2) Inner diameter: D = √(4 × 166.7 / π) = 14.6 mm → nearest larger standard ≥ 16 mm
Frequently Asked Questions
What are the recommended hydraulic line velocities?
Suction line 0.5–1.5 m/s, pressure line 3–6 m/s, return line 2–4 m/s.
What happens if velocity is too high?
Pressure loss, turbulence, heating and noise increase. That is why the diameter is usually rounded up to the next standard.
Why round the diameter up?
The computed diameter is an in-between value; choosing the nearest larger standard keeps velocity on the safe (slightly lower) side.