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Hazen–Williams Head Loss

Also known as C factor head loss

hf=10.67 L Q1.852C1.852D4.8704h_f = \frac{10.67 \, L \, Q^{1.852}}{C^{1.852} D^{4.8704}}
m^0.37/s
sig figs

Worked example: 50 L/s through 100 m of 200 mm at C = 130 → h_f = 1.282 m. Press Try an example to run it live, then adjust anything.

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Where Hazen–Williams Head Loss fits

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Your answer feeds
Total Dynamic HeadNet Positive Suction Head Available (NPSHa)Hydraulic GradientEnergy Balance Between Two Sections with Losses
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See also

Darcy–Weisbach Head Loss: Both use friction head loss and pipe length.Pipe Internal Volume: Both use pipe length and inside diameter.Weymouth Gas Pipeline Flow (Flow from the Pressure Drop): Both use pipe length and inside diameter.Hazen–Williams Velocity: Both use hazen williams c factor.Minor Loss from K Factor: Both use friction head loss.Net Positive Suction Head Available (NPSHa): Both use friction head loss.
4 more relatedTotal Dynamic Head: Both use friction head loss.Energy Balance Between Two Sections with Losses: Both use friction head loss.Energy Loss in a Hydraulic Jump: Both use friction head loss.Hydraulic Gradient: Both use friction head loss.
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Hazen–Williams Head Loss explained

hfQCLD

Allen Hazen and Gardner Williams fitted this in 1905 to thousands of waterworks measurements, and its great virtue is that all the pipe's character collapses into one number, C, that a utility can measure by fire-flow test and track over decades. New plastic runs C = 150, cement-lined ductile iron 140, new steel 130, twenty-year-old unlined cast iron 100 or worse. Push 50 L/s through 100 m of 200 mm pipe at C = 130 and you lose about 1.28 m: comfortably inside the 3 m per 100 m that most distribution standards allow.

The formula is emphatically not general. It is calibrated for water near 15 °C at velocities under about 3 m/s in pipes 50 mm and larger; use it on glycol, on oil, on steam or on hot water and the answer is wrong by an amount nobody can bound, because viscosity appears nowhere in it. That is also its charm: fire-protection codes such as NFPA 13 mandate Hazen–Williams precisely because it needs no fluid properties and no iteration, and every sprinkler hydraulic calculation in North America runs on it. For anything but cool water, use Darcy–Weisbach.

Hazen–Williams Head Loss formula

hf=10.67 L Q1.852C1.852D4.8704h_f = \frac{10.67 \, L \, Q^{1.852}}{C^{1.852} D^{4.8704}}
Where
  • hfh_f= Friction head loss (m)
  • LL= Pipe length (m)
  • QQ= Flow rate (L/min)
  • CC= Hazen–Williams C factor (m^0.37/s)
  • DD= Inside diameter (mm)
In this toolkit

Pipe friction losses

9 formulasDarcy–Weisbach, Hazen–Williams, friction factors, minor losses and equivalent length — every way the trade computes head loss in pipe.

Revised 31 October 2026
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formula.expert. (2026, October 31). Hazen–Williams Head Loss Formula & Calculator. https://formula.expert/solvers/hazen-williams-head-loss

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