Calculation result
Enter values and select Calculate.
Educational planning arithmetic only. Enter your own measured values and properties; these results are not an engineering specification, safety decision, or equipment recommendation.
Formula and method
Darcy–Weisbach major head loss hf = f(L/D) v²/(2g), where f is the Darcy friction factor you enter. Pressure drop ΔP = ρghf. If flow rate is entered, average velocity comes from Q/(πD²/4). See the New Mexico Water Resources Research Institute pipe-network reference.
Worked example
At f = 0.02, L = 10 m, D = 0.05 m, v = 2 m/s, density = 1000 kg/m³ and g = 9.80665 m/s², the major pressure drop is 8000 Pa and the head loss is about 0.8158 m.
Scope and limitations
This models major loss in a straight pipe only. The entered coefficient must be a Darcy factor, not a Fanning factor. Fittings, valves, entrance/exit losses, elevation changes, pump effects, roughness and Reynolds-based factor selection, compressibility, and transient flow are not calculated. Do not use as a pressure-system design approval.
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