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Pneumatics & Hydraulics

Pipe pressure drop calculator (Darcy-Weisbach)

Pressure loss in a pipe or hose for oil or water.

L/min
mm
m
cSt
ISO VG 32 oil ≈32 cSt at 40 °C; water ≈1
kg/m³

Calculating…

How it's calculated

Δp = f × (L/D) × ρv²/2 Laminar (Re < 2300): f = 64/Re Turbulent: f = 0.25 ÷ [log10(ε/3.7D + 5.74/Re^0.9)]²

Hydraulic oil is usually laminar in pressure lines; water is almost always turbulent. Cold oil has far higher viscosity, so pressure drops at start-up can be several times the warm figure. Fittings, bends and valves add losses on top of straight pipe.