What friction factor correlations does this calculator use?

This calculator computes Darcy and Fanning friction factors using three methods: Colebrook-White iteration (industry standard), Swamee-Jain explicit approximation, and Churchill correlation. It also generates an interactive Moody diagram.

What is the difference between Darcy and Fanning friction factors?

The Darcy friction factor is four times the Fanning friction factor (f_Darcy = 4 × f_Fanning). Darcy is more common in pipeline engineering while Fanning is used in chemical engineering. This calculator reports both values.

What is the typical pipe roughness for commercial steel pipe?

Commercial steel and wrought iron pipe has an absolute roughness of 0.0018 inches (0.046 mm). Other common values include galvanized iron at 0.006 in, cast iron at 0.010 in, and PVC/plastic at 0.00006 in.

How do I determine the flow regime from Reynolds number?

Laminar flow occurs at Re 4,000, where the Colebrook-White equation applies.

Pipe Friction Factor Calculator & Moody Diagram

From Flow Conditions

Calculate from velocity, diameter, fluid properties

Direct Input

Enter Reynolds number and relative roughness directly

Fluid & Flow Properties

Input Method

Flow Velocity

ft/s

Fluid Density

lb/ft³

Fluid Preset (optional)

Pipe Properties

Pipe Inner Diameter

Absolute Roughness

Commercial steel = 0.0018 in

Dynamic Viscosity

Pipe Length (optional)

For ΔP calculation

Direct Input

Reynolds Number

Relative Roughness (ε/D)

📚 Learn the Theory

Understand friction factor correlations, Moody diagram interpretation, and flow regime identification

Read Engineering Guide →

📋 Pipe Roughness Reference

Commercial Steel/Wrought Iron: 0.0018 in (0.046 mm)
Galvanized Iron: 0.006 in (0.15 mm)
Cast Iron: 0.010 in (0.26 mm)
Concrete: 0.012–0.120 in (0.3–3.0 mm)
PVC / Plastic: 0.00006 in (0.0015 mm)
Stainless Steel: 0.00007 in (0.002 mm)
Riveted Steel: 0.036–0.36 in (0.9–9.0 mm)

🔬 Flow Regime Guide

Laminar: Re < 2,100 — f = 64/Re
Transition: 2,100 < Re < 4,000 — unstable
Turbulent (smooth): Re > 4,000, low ε/D
Turbulent (rough): Re > 4,000, high ε/D — fully rough zone

Results

Enter parameters and click Calculate to see friction factor results and Moody diagram.

Key Equations

Colebrook-White (1939):

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

Swamee-Jain (1976):

f = 0.25/[log₁₀(ε/(3.7D) + 5.74/Re⁰·⁹)]²

Reynolds Number:

Re = ρVD/μ

Darcy-Weisbach:

ΔP = f(L/D)(ρV²/2gₒ)

Standards: Colebrook (1939), Swamee-Jain (1976), Churchill (1977), Moody (1944), Crane TP-410

Friction Factor & Moody Diagram Calculator

Fluid & Flow Properties

Pipe Properties

Direct Input

📚 Learn the Theory

📋 Pipe Roughness Reference

🔬 Flow Regime Guide

Results

Key Equations

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