Enter the length to fully develop the velocity profile (ft) and the tube diameter (ft) into the Calculator. The calculator will evaluate the Entrance Length. 

Entrance Length Formula

EL = Ie / d


  • EL is the Entrance Length (ft/ft)
  • Ie is the length to fully develop velocity profile (ft)
  • d is the tube diameter (ft)

To calculate the Entrance Length, divide the length to fully develop the velocity profile by the tube diameter.

How to Calculate Entrance Length?

The following steps outline how to calculate the Entrance Length.

  1. First, determine the length to fully develop velocity profile (ft). 
  2. Next, determine the tube diameter (ft). 
  3. Next, gather the formula from above = EL = Ie / d.
  4. Finally, calculate the Entrance Length.
  5. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

length to fully develop velocity profile (ft) = 6.5

tube diameter (ft) = 0.45


What is the significance of calculating the Entrance Length in fluid mechanics?

The Entrance Length is crucial in fluid mechanics because it determines the distance required for the flow to become fully developed inside a tube or pipe. This is important for designing efficient piping systems and for accurate fluid flow analysis.

How does tube diameter affect the Entrance Length?

The tube diameter directly influences the Entrance Length. A larger diameter requires a longer distance for the velocity profile to fully develop, while a smaller diameter means the flow will become fully developed over a shorter distance.

Can the Entrance Length formula be used for any type of fluid?

Yes, the Entrance Length formula can be applied to any type of fluid, but the fluid’s properties, such as viscosity and density, may affect the length required for the velocity profile to fully develop.

Is the Entrance Length the same for laminar and turbulent flow?

No, the Entrance Length varies significantly between laminar and turbulent flow. Laminar flow typically requires a shorter distance to become fully developed compared to turbulent flow, which needs a longer distance due to the chaotic nature of the fluid particles.