Pipe Flow & Velocity Calculator
Calculate flow velocity, Reynolds number, friction factor, and head loss for water and wastewater pipelines using the Darcy-Weisbach equation. Supports uPVC, HDPE, GI, CI, MS, DI, concrete, and RCC pipes.
Free · Darcy-Weisbach · Swamee-Jain · 7 MaterialsPipe Parameters
Uses Darcy-Weisbach equation with Swamee-Jain friction factor. Water at 20°C (ν = 1.004×10⁻⁶ m²/s).
Enter the internal (bore) diameter
If provided, total head loss will be calculated
How to Use This Calculator
- 1Enter the internal pipe diameter in mm (use the bore/internal diameter, not the OD).
- 2Enter the flow rate in m³/hr or L/s and select the pipe material — this sets the roughness value (ε).
- 3Optionally enter pipe length (m) to get total head loss for the pipeline, useful for pump selection.
Formulas Used
# Darcy-Weisbach with Swamee-Jain friction factor
A (m²) = π × D² ÷ 4
v (m/s) = Q (m³/s) ÷ A
Re = v × D ÷ ν [ν = 1.004×10⁻⁶ m²/s at 20°C]
f = 0.25 ÷ [log₁₀(ε/3.7D + 5.74/Re⁰·⁹)]² [Swamee-Jain]
h_f/L = f × v² ÷ (2 × 9.81 × D) [m head per metre]
f = 64 ÷ Re [for laminar flow, Re < 2000]
Pipe Roughness Values (ε)
| Material | Roughness ε (mm) | Common Use |
|---|---|---|
| uPVC / HDPE | 0.0015 | Water supply, effluent lines |
| MS (Mild Steel) | 0.046 | Pumping mains, industrial |
| GI (Galvanised Iron) | 0.15 | Building distribution |
| DI / CI | 0.26 | Water mains, sewage |
| Concrete | 0.3 | Gravity sewers |
| RCC | 1.0 | Large diameter sewers, culverts |
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