Enter the duct design flow (CFM) and the allowable leakage percent (%) into the Duct Leakage Calculator. The calculator will evaluate the Duct Leakage.

## Duct Leakage Formula

The following two example problems outline the steps and information needed to calculate the Duct Leakage.

DL = DF * AL / 100

Variables:

- DL is the Duct Leakage (CFM)
- DF is the duct design flow (CFM)
- AL is the allowable leakage percent (%)

To calculate the duct leakage, divide the duct design flow by the allowable leakage percentage over 100.

## How to Calculate Duct Leakage?

The following steps outline how to calculate the Duct Leakage.

- First, determine the duct design flow (CFM).
- Next, determine the allowable leakage percent (%).
- Next, gather the formula from above = DL = DF * AL / 100.
- Finally, calculate the Duct Leakage.
- After inserting the variables and calculating the result, check your answer with the calculator above.

**Example Problem : **

Use the following variables as an example problem to test your knowledge.

duct design flow (CFM) = 500

allowable leakage percent (%) = 3

DL = DF * AL / 100** **= ?