Calculate duct volume from a round duct’s diameter or a rectangular duct’s width and height plus length, or solve for duct size or length.

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Duct Volume Formula

The following formula is used to calculate the Duct Volume. 

Vd = CSA ร— L
  • Where Vd is the Duct Volume (ft3)
  • CSA is the duct cross-sectional area (ft2) 
  • L is the duct length (ft) 

To calculate the duct volume, multiply the duct area by the duct length.

How to Calculate Duct Volume?

The following example problems outline how to calculate Duct Volume.

Example Problem #1:

  1. First, determine the duct cross-sectional area (ft2).
    1. The duct cross-sectional area (ft2) is given as 3.
  2. Next, determine the duct length (ft).
    1. The duct length (ft) is provided as 60.
  3. Finally, calculate the Duct Volume using the equation above: 

Vd = CSA * L

The values given above are inserted into the equation below:

Vd = 3 * 60 = 180 (ft3)

Example Problem #2: 

For this problem, the variables needed are provided below:

duct cross-sectional area (ft2) = 5

duct length (ft) = 40

This example problem is a test of your knowledge on the subject. Use the calculator above to check your answer. 

Vd = CSA * L = ?