Duct Velocity Calculator

How Duct Velocity Calculator Works

Duct velocity represents the speed of air flowing through an HVAC duct. Proper air velocity is essential for efficient airflow distribution, noise control and system performance.

Important Factors

  • Airflow rate (CFM)
  • Duct diameter
  • Duct cross-sectional area
Velocity Formula

Duct Area = π × (Diameter ÷ 2)²

Air Velocity (FPM) = Airflow (CFM) ÷ Duct Area

Example

Airflow = 1200 CFM
Duct Diameter = 14 inches

Estimated Duct Velocity ≈ 940 FPM

This calculator helps HVAC engineers determine proper duct air velocity during duct design.

Duct Velocity Calculator

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Frequently Asked Questions

1. What is duct velocity in HVAC?

Duct velocity is the speed of air flowing inside an HVAC duct, usually measured in feet per minute (FPM).

2. What is recommended duct velocity?

Typical recommended velocity ranges between 600–900 FPM for supply ducts and 900–1200 FPM for main ducts.

3. Why is air velocity important?

Proper velocity ensures balanced airflow, efficient cooling and reduced noise in HVAC systems.

4. Can high duct velocity cause noise?

Yes. High air velocity can cause duct noise, vibration and increased pressure loss.