Friction Factor Calculator

Enter the fluid velocity, pipe diameter, and kinematic viscosity into the calculate to determine the friction factor.

Friction Factor Formula

The following formula is used to calculate the friction factor in laminar flow.

f = 64 / RE = 64 / (V*D/v)

  • Where f is the friction factor
  • V is the fluid velocity (m/s)
  • D is the diameter of the pipe (m)
  • v is the kinematic viscosity (m^2/s)

In the case of this formula, it can also be written as 64 / RE, where RE is the Reynold’s number = V*D/v


What is a friction factor?

A friction factor is a unitless measure of friction of a fluid moving through a pipe. It’s often used to help calculate energy loss as fluid moves through an opening.

What is Reynolds number?

The Reynolds number is a number , similar to a friction factor, that is a measure of the resistance to flow due to internal resistance as a fluid moves through a pipe.


The following is an example of calculating a friction factor.

  1. First, determine the velocity of the fluid. Measure the velocity of the fluid or calculate it. For this example we will assume a velocity of 25 m/s.
  2. Next, determine the diameter of the pipe. The pipe in this problem is said to be 25m in diameter.
  3. Next, determine the kinematic viscosity. Through empirical data or through published data on the fluid, we find the kinematic viscosity to be 10 m^2/s.
  4. Finally, calculate the friction factor using the formula. f = 64/(25*25/10) = 1.024.
friction factor calculator

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