Nusselt Number Calculator

To find the Nusselt number, enter the values of characteristic length, thermal conductivity, and the heat coefficient in the Nusselt number calculator.


Is This Tool Helpful?


This calculator helps to find different parameters that are involved in the Nusselt number equation. Users can choose between 4 values to calculate any one value. 

What is the Nusselt Number?

It is a dimensionless number that is a ratio of transfer of heat between the convective (to the fluid) to the conductive (within the fluid). 

The name is given after a German scientist Wilhelm Nusselt. It is a function of Reynolds and Prandtl numbers.

Nusselt Number Formula

The formula of Nusselt number:

Nu = h * k / L

In this equation:

Nu = Nusselt number

h = Convection heat transfer coefficient 

k = conductivity coefficient 

L = characteristic length  

Equations related to Nusselt number are: 

For convection:

h = Nu * k / L

For conduction:

k = h * L / Nu

How to calculate the Nusselt number?


Calculate the Nusselt number if:

Convection heat transfer coefficient = h = 15 W/m2-K 

Conductivity coefficient = k = 8 W/m-k

Characteristic length = L = 7 m


Step 1: Write the formula:

Nu = h * k / L

Step 2: Put the values.

Nu = 15 * 8 / 7

Nu = 17.1.43