Reynolds Number Calculator
Calculate Reynolds number and determine flow regime for accurate fluid mechanics analysis and piping system design.
Results
Enter parameters to calculate Reynolds number
Understanding Reynolds Number
The Reynolds number (Re) is a dimensionless quantity that predicts flow patterns in fluid flow situations. It is calculated using the formula: Re = ρ × V × D / μ, where ρ is fluid density, V is velocity, D is characteristic length (pipe diameter), and μ is dynamic viscosity.
Laminar Flow
Re < 2,300
- • Smooth, orderly flow
- • Low energy losses
- • Predictable patterns
Transitional
2,300 < Re < 4,000
- • Unstable regime
- • Unpredictable
- • Avoid in design
Turbulent Flow
Re > 4,000
- • Chaotic mixing
- • Higher energy losses
- • Better heat transfer
Engineering Applications
- • Pipe sizing and design
- • Friction factor determination
- • Heat exchanger design
- • Mixing system analysis
- • Pump selection criteria
- • Flow measurement verification
Important Notes
Reynolds number is critical for determining appropriate calculation methods for friction factor, pressure drop, and heat transfer. Most piping systems operate in the turbulent regime. Consult ASME and ASHRAE standards for specific applications.