AutoEngCalc - Engineering Calculators

Reynolds Number Calculator

Calculate Reynolds number (Re) for pipe, rectangular duct and open channel flow. Instant flow regime classification (laminar, transition, turbulent).

Reynolds Number Re
45000
Water in 100mm pipe, v=1.5 m/s

Reynolds Number (Re)

Featured: Pipe • Duct • Channel • Flow Regime

Flow Regime Indicator

Reynolds number scale

Reynolds Number
Re = ρ v D_h / μ
D_h = 4A / P (hydraulic diameter)

Enter flow parameters to see results

Flow Regime Guidelines

Pipe Flow

Laminar: Re < 2300

Transition: 2300–4000

Turbulent: Re > 4000

Open Channel

Laminar: Re < 500

Transition: 500–2000

Turbulent: Re > 2000

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