Air Duct Pressure Loss Calculator

The Formula

The formula for calculating pressure loss in an air duct is:

\[Pressure Loss (in w.g.) = Friction Factor \times \frac{Duct Length}{100}\]

Where:

• Pressure Loss: The pressure drop in the duct (in inches of water gauge, in w.g.)
• Friction Factor: The friction loss per 100 feet of duct (in inches of water per 100 ft)
• Duct Length: The length of the duct (in feet)

Calculation Steps

1. Determine the friction factor based on duct size, airflow rate, and duct material
2. Multiply the friction factor by the duct length divided by 100

Example Calculation

Let's calculate the pressure loss for a duct with the following parameters:

• Duct dimensions: 12" × 8"
• Duct length: 100 feet
• Airflow rate: 1000 CFM
• Friction factor: 0.08 inches of water per 100 ft

Pressure Loss = 0.08 × (100 ÷ 100) = 0.08 in w.g.

Visual Representation

This visual shows the pressure loss in a duct based on our example calculation.