Friction Factor Calculator (Darcy-Weisbach)

Your details

Internal (hydraulic) diameter of the pipe or duct.
m
Mean (average) fluid velocity in the pipe cross-section.
m/s
Kinematic viscosity = dynamic viscosity / density. For water at 20 °C use 1.004e-6 m²/s; for air at 20 °C use 1.516e-5 m²/s.
m²/s
Mean absolute roughness of the pipe interior. Commercial steel: 0.046 mm; drawn copper/glass: 0.0015 mm; concrete: 0.3-3 mm.
m
Optional. If provided, the head loss and pressure drop are calculated using the Darcy-Weisbach equation.
m
Darcy friction factor (f)Turbulent flow
0.01929

Dimensionless pipe friction factor from the Moody diagram

Reynolds number (Re)149,402
Relative roughness (e/D)0.00046
Flow regimeTurbulent (Re > 4,000)
Head loss (h_f)2.212m
Pressure drop (ΔP)21,696.2Pa
0.01929 f
Very smooth / laminar<0.02Moderate friction0.02-0.04High friction0.04-0.07Very rough0.07+

Darcy friction factor f = 0.01929, Turbulent.

  • Reynolds number 149402 places this flow in the turbulent regime.
  • Relative roughness of 0.000460 is low, so both Reynolds number and roughness influence friction factor in this turbulent regime.
  • Head loss over the specified pipe length is 2.212 m, corresponding to a pressure drop of 21696.2 Pa.

Next stepTo reduce friction losses: increase pipe diameter (dominant effect), smooth the internal surface, or reduce flow velocity.

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