HVAC Airflow and Duct Calculators

Calculators

• Advanced HVAC Duct Sizing Calculator
  Size HVAC ductwork from CFM, available static pressure, total effective length, friction rate, and target air velocity.

Frequently Asked Questions

Why is free area smaller than grille face area?

Blades, frame, filter, and construction block part of the nominal opening.

Why keep return velocity low?

Lower face velocity can reduce grille noise and pressure drop, though actual targets depend on the product and application.

Can several grilles share return airflow?

Yes, when duct and room-return paths are designed to distribute the airflow.

Does this size the return duct too?

No. Use a duct design calculation that includes friction and static pressure.