Static Pressure Calculator

Estimate static pressure loss in a duct system based on airflow, duct size, and system components.

Calculator

Duct Length (ft)

Friction Rate (in w.g. / 100 ft)

Static Pressure

0.00 in. w.g.

Enter values above and calculate.

How It Works

Thi calculator estimates the static pressure loss through a duct run based on the duct length and friction rate. Static pressure is the resistance the fan or air handler must overcome to move air through the system - keeping it within acceptable limits is critical for proper airflow and equipment performance.

Static Pressure (in w.g.) = (Friction Rate × Duct Length) ÷ 100

Where:
Friction Rate = pressure loss per 100 feet of duct in inches of water gauge (in w.g.)
Duct Length = total length of the duct run in feet
100 = normalizes the friction rate from per-100-ft to per-ft
Result = estimated static pressure loss across the duct run in in w.g.

Typical friction rate targets:
Residential systems: 0.08–0.10 in w.g. per 100 ft
Light commercial: 0.10–0.15 in w.g. per 100 ft
High velocity systems: 0.15–0.20 in w.g. per 100 ft

Common example: A 250 ft duct run at 0.08 in w.g. per 100 ft results in 0.20 in w.g. of static pressure loss.