Friction Factor Calculator

Re = ρVD/μ (use Reynolds calculator if unknown)
Internal pipe diameter
Enter 0 for smooth pipe, or specific value (steel: 0.045mm, PVC: 0.0015mm)
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What This Calculator Does

Calculates the Darcy friction factor for pipe flow analysis. Essential for head loss calculations in the Darcy-Weisbach equation.

Key Points:
  • Automatic flow regime detection (Laminar/Transitional/Turbulent)
  • Theoretical solution for laminar flow (f = 64/Re)
  • Smooth pipe equations (Blasius/Prandtl) for ε = 0
  • Swamee-Jain approximation for rough pipes
  • Accounts for pipe roughness and relative roughness (ε/D)
Calculation Steps:
  1. Enter all required parameters
  2. Click "Update Calculation"
  3. Review results and analysis
Formula Variables:
f Friction Factor (-)
Re Reynolds Number (-)
ε/D Relative Roughness (-)
Flow Flow Regime (-)