Pipe Flow Pressure Drop Calculator

Formula

• Re = ρ V D / μ
• h_f = f × (L/D) × V²/(2g)
• ΔP = ρ g h_f
• f from Swamee-Jain (turbulent) or 64/Re (laminar)

About this calculator

Part of our Thermal & Fluids Calculators collection. Heat transfer, pipe flow, Reynolds number, and thermodynamic cycles.

How it works

Pressure drop follows the Darcy-Weisbach equation with velocity from flow rate and pipe area. Friction factor uses laminar 64/Re or a turbulent approximation based on Reynolds number and relative roughness. Head loss converts pressure drop to equivalent fluid column height.

Enter your values in the inputs above and click CALCULATE. Results appear on the right without a page reload. No login and no server upload.

Worked example

50 mm pipe, 100 m, 25 m³/h water, ε=0.15 mm.

1. V = 3.54 m/s, Re ≈ 176 500 (turbulent)
2. f ≈ 0.027 (Swamee-Jain)
3. Head loss ≈ 34.6 m → ΔP ≈ 339 kPa

Result: Pressure drop 339 kPa, hydraulic power loss ~2.35 kW.

When to use

• Estimating pump head for piping systems
• Checking velocity and Reynolds number in pipe design
• Comparing roughness effects on friction factor

Limitations

• Straight pipe only; no fittings, valves, or entrance losses
• Swamee-Jain correlation for turbulent flow
• Assumes incompressible single-phase flow

FAQ

Darcy vs Fanning friction factor?

This calculator uses Darcy friction factor (f_D). Fanning f_F = f_D / 4.

Typical roughness values?

Drawn copper ~0.0015 mm, galvanized steel ~0.15 mm, cast iron ~0.26 mm, concrete ~0.3–3 mm.