Enter the friction factor, length of pipe, the inner diameter of the pipe, and the velocity of flow into the calculator to determine the friction head loss.

Pipe Friction Loss Formula

The following formula is used to calculate the head loss due to friction of flow through a pipe.

hf = f (L/D) * (v^2/2g)
  • Where hf is the head loss (m)
  • f is the friction factor
  • L is the length of pipe (m)
  • D is the inner diameter of the pipe (m)
  • v is the flow velocity (m/s)
  • g is the acceleration due to gravity (m/s^2)

Units of feet can be substituted for meters assuming the proper conversions are done.

Pipe Friction Loss Definition

Pipe friction loss refers to the pressure drop that occurs as a fluid flows through a pipe due to the friction between the fluid and the walls of the pipe.

When fluid flows through a pipe, it experiences resistance from the pipe’s inner surface, which results in a loss of pressure along the length of the pipe.

This phenomenon is important for engineers and designers involved in fluid flow systems as it directly impacts the efficiency and effectiveness of the system.

By understanding pipe friction loss, engineers can accurately calculate the pressure drop and select appropriate pipe sizes, pumps, and other equipment required to maintain the desired flow rate.

As fluid flows through a pipe, it loses energy in the form of pressure due to frictional resistance.

This pressure loss can lead to a decrease in flow rate and may require additional energy, such as increased pump power, to maintain the desired flow.

Pipe Friction Loss Example

How to calculate a pipe friction loss?

  1. First, determine the friction factor.

    Calculate the friction factor between the pipe and the fluid flow.

  2. Next, determine the length and diameter.

    Measure the length and inner diameter of the pipe.

  3. Next, determine the velocity of fluid.

    Measure the fluid velocity moving through the pipe.

  4. Finally, calculate the pipe friction loss.

    Calculate the pipe friction loss using the equation above.


How does pipe material affect friction loss?

Pipe material significantly impacts friction loss because different materials have varying surface roughness levels. Rougher surfaces increase resistance to flow, leading to higher friction losses. Materials such as PVC tend to have smoother surfaces compared to concrete or steel, resulting in lower friction losses.

Can the diameter of the pipe influence the flow rate?

Yes, the diameter of the pipe directly influences the flow rate. A larger diameter reduces the velocity of the fluid for a given flow rate, which in turn reduces the friction loss due to less resistance against the fluid’s flow. This allows for a higher flow rate for the same pressure drop compared to a smaller diameter pipe.

Why is the Reynolds number important in calculating friction loss?

The Reynolds number is a dimensionless quantity that helps predict flow patterns in different fluid flow situations. It is crucial in calculating friction loss because it indicates whether the flow is laminar or turbulent. Laminar flow, which occurs at lower Reynolds numbers, has lower friction losses compared to turbulent flow, which happens at higher Reynolds numbers.

How does temperature affect the friction factor and subsequently friction loss?

Temperature affects the viscosity of the fluid, which in turn influences the friction factor. As temperature increases, the viscosity of most liquids decreases, reducing the friction factor and thus the friction loss. For gases, the effect can be the opposite; increasing temperature may increase viscosity, potentially increasing the friction factor and friction loss.

pipe friction loss calculator
pipe friction loss formula