Duct Velocity Calculator

Enter the airflow and the duct size to get actual air velocity in FPM, velocity pressure, and a check against the recommended band for the application.

Section Parameters

Round, rectangular or flat oval sections.

Airflow (CFM)

Duct shape

Diameter (in)

Check velocity against

Air temperature (°F)

Site elevation (ft)

Velocity Results

Air velocity: 1,132 FPM
Velocity pressure: 0.080 in. w.g.

Cross-sectional area: 1.767 ft²
Circular equivalent diameter: 18.0 in
Velocity in equivalent round duct: 1,132 fpm
Hydraulic diameter / perimeter: 18.0 in / 56.5 in
Aspect ratio: n/a
Air density used: 1.1998 kg/m³

Inside the 1000–1600 fpm band for this application.

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Important Disclaimer

This calculator is for preliminary design guidance only. Final duct sizing, construction, and installation must be performed by qualified professionals and comply with applicable codes and standards.