Pipe Reynolds Number

Screen circular pipe flow regime from average velocity, inside diameter, and viscosity.

Concept

Results

Enter the inputs and select Calculate.

Inputs

Viscosity input modeAverage velocity *

Use cross-sectional average velocity.Pipe inside diameter *

Use actual inside diameter, not nominal pipe size.Kinematic viscosity *

Used in kinematic-viscosity mode.Density *

Used with dynamic viscosity mode.Dynamic viscosity *

Used with density in dynamic-viscosity mode.

Formula & Variables

Re =ρVDμ=VDν

Re: Reynolds number; [1]
V: Average velocity; [m/s]
D: Inside diameter; [m]
μ: Dynamic viscosity; [Pa*s]
ν: Kinematic viscosity; [m^2/s]

Assumptions

Internal flow in a circular pipe.
Velocity is the average over the pipe cross section.
Fluid properties are evaluated at the relevant operating conditions.

⚠ Limitations

Noncircular passages require a hydraulic-diameter or flow-area method appropriate to the geometry.
Regime thresholds are screening guidance, not exact physical boundaries.
Compressibility and property variation are not handled.