Friction Factor Calculator
Calculate the Darcy friction factor using Colebrook-White and Swamee-Jain equations for accurate pressure drop analysis in piping systems.
Dimensionless flow parameter
Steel: 0.045mm, PVC: 0.0015mm, Cast iron: 0.25mm
Results
Enter parameters to calculate friction factor
Understanding Friction Factor
The Darcy friction factor (f) is a dimensionless quantity used in the Darcy-Weisbach equation to calculate pressure drop due to friction in pipes. It depends on Reynolds number and relative pipe roughness (ε/D).
Calculation Methods
Laminar Flow (Re < 2,300)
f = 64 / Re
The friction factor is independent of pipe roughness in laminar flow and only depends on Reynolds number.
Turbulent Flow (Re > 4,000)
Swamee-Jain Approximation:
f = 0.25 / [log₁₀(ε/3.7D + 5.74/Re^0.9)]²
This explicit approximation of the implicit Colebrook-White equation is accurate within 1% for most engineering applications.
Common Pipe Roughness Values
| Material | Roughness (mm) | Roughness (mil) |
|---|---|---|
| Steel (new) | 0.045 | 1.8 |
| Steel (aged) | 0.15 | 6 |
| PVC | 0.0015 | 0.06 |
| Copper | 0.0015 | 0.06 |
| Cast Iron (new) | 0.25 | 10 |
| Concrete | 0.3-3.0 | 12-120 |
Engineering Application
The friction factor is used in the Darcy-Weisbach equation: ΔP = f × (L/D) × (ρV²/2)to calculate pressure drop in pipes. Accurate friction factor determination is critical for proper pump sizing, energy cost analysis, and system optimization.