Duct Sizing Calculator

Duct Sizing

Calculate the correct HVAC duct dimensions based on airflow requirements, friction rate, and duct shape for efficient air distribution in heating and cooling systems.

Required Airflow (CFM)

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

Duct Shape

Max Air Velocity (fpm)

Formula

Cross-Section Area = (CFM / Max Velocity) x 144; Round Diameter = sqrt(Area / Pi) x 2; Rectangular Equivalent = Based on equal friction method; Actual Velocity = (CFM x 144) / Actual Area

Frequently Asked Questions

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