MAXScanner physics & engineering calculator
Reynolds Number Calculator — Flow Regime, Dynamic & Kinematic Viscosity
Calculate Reynolds number from velocity, characteristic length and either kinematic viscosity or density plus dynamic viscosity. Classify common circular-pipe flow and see the alternate viscosity value.
Last updated: September 17, 2026
Results
Enter velocity, length and either kinematic viscosity or density + dynamic viscosity
Formula, example and assumptions
Re=ρvL/μ=vL/ν; ν=μ/ρ.
Water near room temperature with v=1 m/s, D=0.1 m and ν≈1×10⁻⁶ m²/s gives Re≈100,000, well into the common turbulent-pipe range.
- Pipe thresholds near 2,300 and 4,000 are guides for internal circular flow, not universal transition limits.
- Use fluid properties at the actual operating temperature and a geometry-appropriate characteristic length.
Frequently asked questions
Is Reynolds number dimensionless?
Yes. Consistent units cancel, leaving a dimensionless ratio of inertial to viscous effects.
Which viscosity should I enter?
Use kinematic viscosity directly, or choose density plus dynamic viscosity; the two forms are mathematically equivalent.