Result

Reynolds number

74,850

Fluid density (ρ)

998 kg/m³

Flow velocity (v)

1.5 m/s

Characteristic length (pipe diameter) (L)

0.05 m

Dynamic viscosity (μ)

0.001 Pa·s

Flow regime (pipe)

Turbulent

How it was calculated

Re = ρ × v × L ÷ μ
Re = 74,850

Defaults are water at about 20 °C. Regime thresholds are for flow in a round pipe.

How to use the Reynolds Number Calculator

Pick what to solve for.
Enter the fluid density, velocity, pipe diameter and viscosity.
Read Re and the flow regime.

What does this tool do?

The Reynolds number compares inertial forces to viscous forces in a flowing fluid. Low values mean smooth, layered (laminar) flow; high values mean chaotic, turbulent flow.

For flow in a round pipe, Re below about 2,300 is laminar and above about 4,000 is turbulent. Defaults are water at 20 °C in a 5 cm pipe.

Why use it?

Flow regime classification.
Solve for any variable.
Water defaults.

The formula

Re = ρ v L ÷ μ

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Last reviewed October 4, 2026 by the M2Toolkit team.