Water Pressure Loss Calculator

Calculate pressure loss (head loss) in pipes using the Darcy-Weisbach equation combined with the Colebrook-White equation for friction factor.

Flow Rate (L/s)

Pipe Internal Diameter (mm)

Pipe Length (m)

Pipe Roughness ε (mm)

Water Temperature (°C)

Results will appear here.

Darcy-Weisbach Equation (head loss):

h_f = f · (L / D) · V² / (2g)

where: f = Darcy friction factor, L = pipe length (m), D = internal diameter (m), V = mean flow velocity (m/s), g = 9.80665 m/s²

Flow Velocity: V = Q / A = Q / (π D² / 4)

Reynolds Number: Re = V · D / ν

Colebrook-White Equation (turbulent flow, Re ≥ 4000):

1 / √f = −2 · log₁₀( ε/(3.7·D) + 2.51 / (Re · √f) )

Solved iteratively; initial guess from Swamee-Jain: f = 0.25 / [log₁₀(ε/(3.7D) + 5.74/Re⁰·⁹)]²

Laminar flow (Re < 2300): f = 64 / Re

Pressure Loss: ΔP = ρ · g · h_f (Pa)

Kinematic Viscosity (Andrade equation): μ = 2.414×10⁻⁵ · 10^(247.8 / (T + 140)) Pa·s; ν = μ / ρ

Steady-state, incompressible, fully developed pipe flow.
Circular cross-section pipe with uniform roughness.
Only major (friction) losses are calculated; minor losses (fittings, bends, valves) are not included.
Transitional flow (2300 ≤ Re < 4000) uses the Colebrook-White equation as an approximation; results in this range carry higher uncertainty.
Water density modelled as ρ = 999.842 − 0.0622T − 0.00354T² (kg/m³), valid 0–100 °C.
Dynamic viscosity via Andrade equation; accurate to ±1% over 0–100 °C.
References: Moody (1944); Colebrook & White (1937); White, F.M. — Fluid Mechanics, 8th ed.; Swamee & Jain (1976) for explicit friction factor approximation.

In the network