Friction Loss Calculator
Compute head loss and pressure drop in pipes using the Darcy–Weisbach equation.
How to Use This Calculator
Enter f, L, D, v
Get f from the Friction Factor calculator or charts; use SI units.
Optionally set density
ρ defaults to 1000 kg/m³ (water). Adjust for other fluids.
Calculate
View head loss in meters and pressure drop in Pascals.
Formula
hf = f · (L/D) · (v² / 2g)
ΔP = ρ g hf = f · (L/D) · (ρ v² / 2)
Where: f = Darcy friction factor, L = length (m), D = diameter (m), v = velocity (m/s), g = 9.80665 m/s², ρ = density (kg/m³).
Example: f = 0.02, L = 50 m, D = 0.1 m, v = 2 m/s → hf ≈ 1.02 m; for water, ΔP ≈ 10000 Pa.
About Friction Loss Calculator
Head loss estimation is essential for pump sizing and pipeline design. The Darcy–Weisbach formulation is widely applicable across laminar and turbulent flow when f is known.
- Includes only major losses; fittings and valves cause additional minor losses.
- Use the Friction Factor calculator to estimate f from Re and roughness.
Frequently Asked Questions
Are minor losses included?
No. Use K-factors for fittings and add K v²/(2g) to head loss.
Can I enter flow rate instead of velocity?
Convert using v = Q/A where A = π(D/2)².
What friction factor is used?
You supply f (Darcy). Compute it via charts or the companion calculator.