Created By : Naaz Fatima

Reviewed By : Phani Ponnapalli

Last Updated : Apr 10, 2023

The User-friendly Reynolds Number Calculator tool displays the Reynolds number which is used to determine whether the fluid is laminar or turbulent. You just need to provide data in the input fields of the calculator and hit the calculate button to get the Raynolds number of the liquid easily.

Choose a Calculation
Fluid density (ρ)
Fluid velocity (u)
characteristic linear dimension (L)
Dynamic viscosity (μ)

Steps to Calculate Reynolds Number

The step by step detailed explanation on how to calculate the Reynolds number of a fluid is given below. Make use of these guidelines and solve the questions easily.

  • Make a note of the given details in the question.
  • Multiply the fluid density, fluid velocity and characteristic linear dimension.
  • Divide the product by dynamic viscosity to get the Reynolds number.
  • Otherwise, multiply the velocity of the fluid with the characteristic linear dimension.
  • Divide the result by the kinematic viscosity of the fluid to obtain the Reynolds number.

Reynolds Number Formula

Reynolds number is a dimensionless quantity that is used to check whether the type of flow pattern is laminar or turbulent while flowing through a pipe. It is defined as the ratio of the inertia force to the viscous force.

The Reynolds number equation is

Re = (ρ * u * L)/μ or Re = (u * L)/v


Re is the Reynolds number

ρ is the density of the fluid

u is the fluid velocity

L is the characteristic linear dimension

╬╝ is the dynamic viscosity of the fluid

v is the fluid kinematic viscosity (v = μ/ρ)


Question: Find the Reynolds number, if the fluid has viscosity 0.5 Ns/m┬▓ and relative density of 750 kg/m┬│ through a pipe of 15 mm with a velocity of 3 m.


Given that

Viscosity of the fluid ╬╝ = 0.5 Ns/m┬▓

Fluid density ρ = 750 kg/m³

Diameter of the fluid L = 15x10-3 m

Fluid velocity u = 3 m

Reynolds number formula is Re = (ρ * u * L)/μ

Re = (750 x 3 x 15x10-3)/0.5

= 67.5

Therefore, Reynolds number of the fluid is 67.5 and the flow of the fluid is laminar flow.

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Frequently Asked Questions on Reynolds Number Calculator

1. What is the turbulent flow?

Turbulent flow is usually employed when Re > 3000. It is dominated by inertial forces and characterized by chaotic eddies and other flow instabilities.

2. What is the laminar flow?

Laminar flow occurs when viscous forces are dominant and characterized by smooth and constant fluid motion. Reynolds number for laminar flow is Re < 2100.

3. How to calculate Reynolds number?

The formula to find Reynolds number is inertial force/viscous force or ρuL/μ. Put the values in the formula and perform the operations to check the Reynolds number.

4. What is the role of Reynolds number?

Reynolds number is useful to predict flow patterns in different fluid flow situations. The lowest Reynolds number means the flow is laminar and the high Reynolds number means turbulent flow.