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# Knudsen Number Calculator

Select the quantity that you want to calculate & write the values in the below tabs and hit on the calculate button to determine the value of the selected terms.

Table of Contents:

**Formula**

**Knudsen Number :**

Kn = λ/L

**Mean Free Path :**

λ = Kn*L

**Representative Physical Length Scale :**

L = λ/ Kn

**Where,**

Kn = Knudsen Number,

λ = Mean Free Path,

L = Representative Physical Length Scale.

The Knudsen Number refers to the dimensionless number. The Knudsen Number is defined as the ratio of the molecular mean free path length to a representative physical length scale. In short, the Knudsen Number refers to the ratio of the mean free path length of the molecules of a fluid to a characteristic length. It is used to describe the flow of the low density gases.

This Advanced Online** **Knudsen Number Calculator is used to calculate the ratio of the mean free path length of the molecules of a fluid to a characteristic length.

__Example__:

Calculate the Knudsen Number for the given details.

Mean Free Path (λ) = 25 m

Representative Physical Length Scale (L) = 20 m

__Solution__:**Apply Formula:**

Kn = λ/L

Kn = 25/20**Kn = 1.25**

**References: **

- Definition of Knudsen number | encyclopedia.
- Mean free path | LibreTexts.