Reynolds Number Calculator

Enter the required values in the input boxes below to find the Reynolds number using Reynolds number calculator.


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Reynolds number formula

The Reynolds number equation can be expressed as:

Re = ρ u L / μ


Re = u L / ν


Re represents Reynolds Number,

ρ refers to the density,

L is the characteristic length,

u is the velocity,

μ is the dynamic viscosity,

ν = μ / ρ = kinematic viscosity.

Reynolds number calculator is an online tool used in fluid mechanics for Reynolds number calculation. It can be used to calculate the:

  • Reynolds number
  • Density
  • Velocity
  • Viscosity, and
  • Characteristic length

Let’s find out Reynolds number definition, how to find Reynolds number, formula of Reynolds number, and the difference between laminar flow and turbulent flow.

What is Reynolds number?

The Reynolds number is a ratio that helps predict flow patterns in different fluid flow conditions. At high Reynolds numbers, flows tend to be turbulent, whereas at low Reynolds numbers, flows tend to be dominated by laminar flow.

There are no Reynolds number units because it is a dimensionless parameter. In other words, Reynolds number is a unit less quantity.

Laminar vs turbulent flow

The laminar flow refers to the flow of a fluid streaming in parallel layers. In laminar flow, fluid flows without having any disruption. While, turbulent flow refers to the fluid not flowing in parallel layers due to the change in velocity, pressure, etc. It flows in mixed layers across the tube.

How to calculate Reynolds number?

To calculate Reynolds number, follow the steps below:


If a fluid is flowing with a velocity of 5.2 m, having viscosity of 0.2 Ns/m2, density of 500 kg/m3, in a pipe with a diameter of 6 m, find the Reynolds number for the fluid?


Step 1: Identify and write down the values.

μ = 0.2 Ns/m2

u = 5.2 m

ρ = 500 kg/m3

L = 6 m

Step 2: Place the values in equation of Reynolds number and solve the equation.

Re = ρ u L / μ

Re = (500 × 5.2 × 6) / 0.2

Re = 78,000

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