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Pipe Pressure Loss

🌡️ Energy & Fluids · Friction loss, Reynolds number, and flow regime via the Darcy-Weisbach equation

🧮 Calculate∑ Formula✅ Verification📚 Sources

Flow Rate Q (m³/h)

Inner Diameter D (mm)

Pipe Length L (m)

Roughness ε (mm)

Density ρ (kg/m³)

Viscosity μ (mPa·s)

Flow velocity v1.105 m/s

Reynolds number Re88,066

Flow regimeTurbulent

Friction factor f0.02101

Pressure loss Δp16.01 kPa

Head loss hL1.635 m

Δp = f·(L/D)·½ρv² — f: 64/Re for laminar, Swamee-Jain for turbulent

💡 Defaults are for 20 °C water and commercial steel pipe (ε = 0.045 mm). Viscosity (mPa·s = cP) keeps the same numeric value in both systems and isn't converted.

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\Delta p = f\,\frac{L}{D}\cdot\frac{1}{2}\rho v^2

The pressure a fluid loses to friction in a pipeline affects many engineering decisions, from pump selection to energy cost. The Darcy-Weisbach equation is the standard way to calculate this loss, but the friction factor (f) itself is calculated differently depending on the flow regime.

Laminar flow (Re < 2300): the friction factor is calculated directly in closed form as f = 64/Re — independent of roughness.

Turbulent flow (Re > 4000): the classic Colebrook equation is not closed-form (f appears on both sides of the equation and requires an iterative solution). The explicit formula published by Swamee and Jain in 1976 eliminates the need for iteration, allowing direct calculation — this tool uses that formula.

Economic velocity rule of thumb: for water lines, the typical economic velocity range is 1–3 m/s, balancing excessive pressure loss against an oversized (expensive) pipe diameter.

📖 Sourced Formula · Single Verification

This tool's formula is based on a reliable source (see the Sources tab below) and has been checked against a hand-computed numerical example. A second, independent literature cross-check has not yet been added. As with any engineering calculation, we recommend independently confirming results before relying on them for critical decisions.

[4] White, Frank M.. Fluid Mechanics, 8 ed.. McGraw-Hill, 2016. ↗
[8] Swamee, P. K. and Jain, A. K.. "Explicit Equations for Pipe-Flow Problems". Journal of the Hydraulics Division, 102(5), 657--664. 1976. ↗

Pipe Pressure Loss — EngineersLab calc card

Formula: Δp = f·(L/D)·½ρv²

Sources: [4] Fluid Mechanics; [8] Explicit Equations for Pipe-Flow Problems

Tool version: 1.1.0 · Date:

Source URL: https://engineerslab.com.tr/en/araclar/boru

Results are for educational and preliminary-sizing purposes; final engineering design decisions must reference the relevant standards and a licensed engineer's approval.