Friction Loss Calculator

Calculate pipe friction loss using the Darcy-Weisbach equation and a Haaland friction factor approximation.

Calculator

Velocity —
Reynolds number —
Friction factor —
Straight pipe loss —
Local losses —
Total head loss —
Total pressure drop —

Formula

Pipe friction loss is calculated using Darcy-Weisbach:

hf = f · L/D · v²/(2g)
Δp = ρ · g · hf

Where:

  • hf = friction head loss [m]
  • f = Darcy friction factor
  • L = pipe length [m]
  • D = pipe inside diameter [m]
  • v = velocity [m/s]
  • Δp = pressure drop [Pa]

Engineering note

This calculator estimates straight-pipe friction loss and simple local losses from fittings using K values. Elbows, valves, strainers, reducers and entrance/exit losses can significantly increase total suction losses. For final pump head calculation, verify K values or equivalent lengths according to the project standard, fitting type and manufacturer data.