Enter the volumetric air flow rate and the cross-sectional area of the duct into the calculator to determine the air velocity.

Air Velocity Formula

The following equation is used to calculate the Air Velocity.

Vair = AFR / DA

  • Where Vair is the air velocity (ft/s)
  • AFR is the air flow rate (ft^3/s)
  • DA is the air duct area (ft^2)

To calculate air velocity, divide the air flow rate by the duct area.

What is an Air Velocity?


An air flow velocity describes the linear speed at which air flows through an enclosed duct.

How to Calculate Air Velocity?

Example Problem:

The following example outlines the steps and information needed to calculate Air Velocity.

First, determine the air flow rate. In this example, the air flow rate is found to be 50 ft^3/2.

Next, determine the air duct area. For this problem, the air duct area is found to be 10 ft^2.

Finally, calculate the Air Velocity using the formula above:

Vair = AFR / DA

Vair = 50 / 10

Vair = 5 ft/s