HVAC ENGINEERING TOOL

Duct Airflow / Velocity / Area Calculator

Solve any missing quantity from duct airflow, internal gross area and air velocity.

Free calculator — authorized account required

Create or sign in to your free professional account. Calculator access is activated only after the applicable Leal approval policy is satisfied; engineering method and reference content remain visible.

Formula / Method

Q = A × V

Engineering Method & Assumptions

Area is internal gross duct cross-sectional area.
No grille free-area factor.
No shape-equivalence or equal-friction sizing.

Applicability: This relationship does not calculate pressure drop, friction rate, fitting losses, or duct-system performance.

WHEN TO USE THIS TOOL

Useful during airside & ventilation work.

Quick-check airflow, velocity, room-air-change or ventilation relationships during design reviews.
Compare alternate design conditions before moving into detailed equipment or duct selection.
Use as a transparent check alongside project criteria, applicable standards and manufacturer data.

Frequently asked questions

What area should I enter?

Enter the internal gross cross-sectional area of the duct.

Does the tool account for grille free area?

No. Apply manufacturer free-area data separately when evaluating a grille or louver.

Does this size an equal-friction duct?

No. It only solves the volumetric relationship Q = A × V.