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Head Loss Calculator

Calculate pipe friction head loss with the Darcy–Weisbach equation.

Head loss
4.079 m
Darcy–Weisbach: hf = f · (L / D) · v² / (2g). Enter pipe geometry and friction factor to compute energy loss.
Head loss (metres)
4.079 m
Loss per 100 m of pipe
4.079 m

How it works

  1. 1Enter the Darcy friction factor f (typically 0.015–0.04; use a Moody chart).
  2. 2Provide the pipe length, internal diameter, and mean flow velocity.
  3. 3The calculator applies hf = f·(L/D)·v²/(2g) and shows total loss and loss per 100 m.

Use cases

  • Sizing pump head for water-supply or irrigation systems.
  • Checking whether a pipeline can deliver the required flow without excessive drop.
  • Comparing head loss for different pipe diameters or materials.

Frequently asked questions

What is the Darcy–Weisbach equation?

hf = f·(L/D)·v²/(2g), where f is the Darcy friction factor, L the length, D the diameter, v the velocity, and g = 9.807 m/s². hf is the head loss in metres.

How do I find the friction factor f?

For turbulent flow use the Moody chart or Colebrook–White equation with relative roughness and Reynolds number; smooth steel near Re ≈ 1e5 gives f ≈ 0.018. Laminar flow (Re < 2300) uses f = 64/Re.

Worked example: 100 m of 100 mm pipe at 2 m/s, f = 0.02?

hf = 0.02 × (100/0.1) × 2² / (2 × 9.807) ≈ 4.08 m of head lost to friction over the run.

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