🌬️Duct Velocity Calculator

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What is Duct Velocity?

Duct velocity is the speed at which air moves through a duct system. It’s a critical parameter in HVAC design, measured in metres per second (m/s) or feet per minute (FPM).

Duct Velocity Formula

V = Q / A

  • V = Velocity (m/s)
  • Q = Volumetric flow rate (m³/s)
  • A = Cross-sectional area of duct (m²)

How to Calculate Duct Velocity

  1. Measure or obtain the air flow rate (Q).
  2. Measure the duct’s inner cross-sectional area (A).
  3. Ensure consistent units (convert CFM → m³/s if needed).
  4. Apply the formula V = Q / A.
  5. Compare the result with recommended limits (e.g., 2–10 m/s for supply ducts).

Frequently Asked Questions

Why is duct velocity important?

High velocity increases noise and pressure drop; low velocity may not distribute air effectively.

What is the ideal duct velocity?

Supply: 6–10 m/s; Return: 4–7 m/s; Low-velocity systems: <3 m/s.

Can I use this calculator for round and rectangular ducts?

Yes—just input the correct cross-sectional area for either shape.

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