Reynolds Number Calculator
Reynolds Number (Re) = ρvL/μ
Length Unit
Velocity Unit
Viscosity Unit
Density Unit
Common Fluid Presets
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Reynolds Number Calculation Result
Reynolds Number: 0
Flow Regime
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0 m/s
Fluid Velocity
0 m
Characteristic Length
0 kg/m³
Fluid Density
0 Pa·s
Fluid Viscosity
About Reynolds Number
The Reynolds number (Re) is a dimensionless quantity used to predict flow patterns in fluid dynamics. It is defined as the ratio of inertial forces to viscous forces and helps determine if a flow is laminar, transitional, or turbulent.
Re = ρvL/μ = vL/ν
Where:
- ρ = Fluid density (kg/m³)
- v = Fluid velocity (m/s)
- L = Characteristic length (m)
- μ = Dynamic viscosity (Pa·s)
- ν = Kinematic viscosity (m²/s) = μ/ρ
Flow Regimes
The Reynolds number provides critical information about the flow regime:
- Re < 2000: Laminar flow (smooth, orderly)
- 2000 ≤ Re ≤ 4000: Transitional flow
- Re > 4000: Turbulent flow (chaotic, disordered)
Usage Instructions
- Enter the fluid velocity, characteristic length, density, and viscosity
- Use the fluid presets for common substances
- Choose appropriate units from the dropdown menus
- Click "Calculate Reynolds Number" to get results
- The calculator will display the Reynolds number and indicate the flow regime