Reynolds Number Calculator
Calculate Reynolds number for pipe, duct, open-channel or flat-plate flow and classify laminar, transitional or turbulent regimes.
Reynolds number
Reynolds number compares inertial and viscous effects in a flow. It is commonly used to estimate whether flow is laminar, transitional or turbulent.
Use either kinematic viscosity or density with dynamic viscosity.
- Re — Reynolds number for the selected geometry.
- v — average flow velocity.
- L — characteristic length or hydraulic diameter.
- nu — kinematic viscosity.
- rho — fluid density.
- mu — dynamic viscosity.
Regime thresholds
For internal pipe and duct flow, values below about 2300 are usually laminar and above about 4000 are turbulent. Transition depends on disturbances, roughness and inlet conditions.
Frequently Asked Questions
Sources and References
- Reynolds Number CalculatorSimScale
- Reynolds Number CalculatorEngLab
- Reynolds NumberEngineering ToolBox
Calculations are based on the listed reference sources. Links open in a new tab.
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