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Pipe Pressure Drop

Darcy-Weisbach: Δp = f·(L/D)·(ρv²/2). Friction factor is 64/Re when laminar (Re < 2300), otherwise the Swamee-Jain explicit fit to Colebrook. Straight pipe only — add fittings as equivalent length.

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Inside Ø (mm)

Flow (L/min)

Length (m)

Density ρ (kg/m³)

Viscosity µ (Pa·s)

Roughness ε (mm)

Fittings ΣK

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Velocity

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Reynolds

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Regime

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Friction Δp

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Fittings Δp

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Head loss

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Tap a fitting to add its K. Water at 20 °C: ρ 1000, µ 0.001. Drawn steel ε ≈ 0.045 mm; PVC ≈ 0.0015.

Straight-pipe, steady, incompressible flow. A helper, not a substitute for engineering judgment.