Pipe Flow Calculator

Calculator

Methods

Properties

Standards

FAQ

Select calculation type and enter known parameters to solve for unknown values using Hazen-Williams and Darcy-Weisbach equations.

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Flow Rate

Calculate Q from pressure & diameter

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Pressure Drop

Calculate ΔP from flow & diameter

⭕

Pipe Sizing

Calculate D from flow & pressure

⚡

Velocity

Calculate V from flow & diameter

Fluid Type

Pipe Material

Calculation Method

Flow Visualization

Water Flow

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Select parameters to see flow characteristics

Calculation Methods

Different methods for calculating pipe flow based on application and fluid properties.

🌊 Hazen-Williams Equation

Q = 0.2083 × C × D^2.63 × S^0.54

Best for: Water flow in pipes larger than 2 inches
Variables: Q = flow rate (ft³/s), C = roughness coefficient, D = diameter (ft), S = slope (ft/ft)
Accuracy: ±5% for water at normal temperatures

⚙️ Darcy-Weisbach Equation

ΔP = f × (L/D) × (ρV²/2)

Best for: All fluids, all pipe sizes, most accurate
Variables: ΔP = pressure drop, f = friction factor, L = length, D = diameter, ρ = density, V = velocity
Accuracy: ±2% when friction factor is known accurately

🏞️ Manning's Formula

V = (1/n) × R^(2/3) × S^(1/2)

Best for: Open channel flow, large pipes, gravity flow
Variables: V = velocity, n = Manning's coefficient, R = hydraulic radius, S = slope
Accuracy: ±10% for typical applications

Reynolds Number Analysis

🔬 Reynolds Number

Re = (ρ × V × D) / μ

Laminar Flow: Re < 2300 (smooth, predictable flow)
Transitional: 2300 < Re < 4000 (unstable flow)
Turbulent Flow: Re > 4000 (chaotic, well-mixed flow)

Fluid Properties

Physical properties of common fluids used in pipe flow calculations.

Common Fluids at 20°C (68°F)

💧 Water

Density: 998 kg/m³

Viscosity: 1.002 × 10⁻³ Pa·s
Most common fluid for hydraulic calculations.
Incompressible for most applications.

🛢️ Oil (SAE 30)

Density: 920 kg/m³

Viscosity: 0.1 Pa·s
High viscosity affects pressure drop significantly.
Temperature sensitive properties.

⛽ Gasoline

Density: 750 kg/m³

Viscosity: 0.6 × 10⁻³ Pa·s
Low viscosity, low density.
Volatile, vapor pressure considerations.

🔥 Natural Gas

Density: 0.8 kg/m³

Viscosity: 11 × 10⁻⁶ Pa·s
Compressible gas flow.
Requires special gas flow equations.

💨 Air

Density: 1.2 kg/m³

Viscosity: 18 × 10⁻⁶ Pa·s
Compressible for high velocities.
HVAC and pneumatic systems.

🔧 Hydraulic Oil

Density: 850 kg/m³

Viscosity: 32 × 10⁻³ Pa·s
Industrial hydraulic systems.
High pressure applications.

Pipe Standards

Standard pipe sizes and roughness values for different materials.

Standard Pipe Sizes (Nominal)

Roughness Values

🔧 Commercial Steel

ε = 0.045 mm

C = 120 (Hazen-Williams)
Most common industrial piping.
New, clean steel pipes.

🏭 Cast Iron

ε = 0.26 mm

C = 100 (Hazen-Williams)
Water distribution systems.
Corrosion increases roughness.

🏗️ Concrete

ε = 0.3-3 mm

C = 120-140 (Hazen-Williams)
Large diameter pipes.
Finish quality affects roughness.

🔌 PVC/Plastic

ε = 0.0015 mm

C = 150 (Hazen-Williams)
Very smooth surface.
Chemical resistant applications.

🥉 Copper

ε = 0.0015 mm

C = 130-140 (Hazen-Williams)
Plumbing applications.
Corrosion resistant.

✨ Stainless Steel

ε = 0.002 mm

C = 140-150 (Hazen-Williams)
Food grade, pharmaceutical.
Very smooth, hygienic.

Frequently Asked Questions

Which calculation method should I use? Darcy-Weisbach for accuracy, Hazen-Williams for water systems, Manning's for open channels.
What affects pressure drop in pipes? Flow rate, pipe diameter, length, roughness, fluid viscosity, and fittings.
How do I handle gas flow? Use compressible flow equations for high velocities (Mach > 0.3) or pressure ratios > 2:1.
What is the maximum recommended velocity? Water: 3-5 m/s, Oil: 1-3 m/s, Gas: <20 m/s to avoid noise and erosion.
How do fittings affect pressure drop? Add equivalent length or use K-factors. Typical values: 90° elbow = 30D, valve = 10-50D.
What about pipe aging? Roughness increases over time. Apply aging factors: steel +20%, cast iron +50% after 20 years.
How accurate are these calculations? ±2-5% for Darcy-Weisbach, ±5-10% for Hazen-Williams with proper inputs.
What units does the calculator use? Supports metric and imperial units with automatic conversion between systems.

🚰 Pipe Flow Calculator