About the Ductwork Calculators
Ductwork calculators help HVAC engineers size and check duct runs. This section includes tools for estimating the static pressure of a duct run from its straight length, fittings, airflow, and dimensions, sizing round duct for a target friction rate, and solving for airflow, diameter, or velocity in a round duct. Use them during layout to keep velocities and pressure losses within design limits, when selecting a fan or unit to confirm the external static pressure it must overcome, and in the field to check that installed ductwork can deliver the design airflow. Each tool applies standard duct friction relationships, including equivalent-diameter conversion for rectangular duct and equivalent-length allowances for elbows, so results line up with published duct design references.