Enter the velocity of the air and the cross-sectional area the air is flowing through into the calculator to determine the airflow rate.

Air-Flow Formula

The following formula is used to calculate the volumetric air-flow rate.

AF = V*A

  • Where AF is the volumetric air flow (m^3/s)
  • V is the velocity of the air (m/s)
  • A is the cross-sectional area the air is moving through (m^2)

The airflow is sometimes referred to as the CFM. CFM refers to the units of cubic feet per minute. For the formula above, this would mean the velocity of the air is in feet per minute, and the cross-sectional area is in feet squared.

Air-Flow Definition

Airflow is defined as the volume of air that is moving through a cross-sectional area per unit of time.

How to calculate airflow?

Example Problem #1:

First, determine the velocity of the air. In this example, the air is measured to be moving at a speed of 2 feet per minute.

Next, determine the cross-sectional area the air is moving through. In this case, the air is moving through a duct that has an opening area of 7 square feet.

Finally, calculate the air-flow speed using the formula above:

AF = V*A

= 2*7

= 14 cubic feet per minute. (CFM)

Example Problem #2:

In this next example, the air is measured to be moving at a rate of 3 feet per second (ft/s). The area it is moving through is measured to be 3 square feet (ft^2).

Using the formula above:

AF = V*A

= 3*3

= 9 cubic feet per second (ft^3/s)

To convert into CFM, multiply this result by 60.

= 9*60 = 540 (ft^3/min)

air flow calculator