CFM calculator

Calculate volumetric airflow in CFM from duct area × average air velocity.

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Duct cross-section area (ft²)

Average air velocity (ft/min)

Answer

…

Calculate volumetric airflow in CFM from duct area × average air velocity.

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Precision and calculation record

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Formula and assumptions

Use average velocity across the section, not a single unrepresentative point. This is a flow relation, not room ventilation, pressure-drop or HVAC equipment sizing.

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Updated 2026-09-26

Using CFM calculator

Calculate volumetric airflow in CFM from duct area × average air velocity.

Use average velocity across the section, not a single unrepresentative point. This is a flow relation, not room ventilation, pressure-drop or HVAC equipment sizing.

Next: Flow rate calculator

A worked example

Example inputs: duct cross-section area (ft²) = 2, average air velocity (ft/min) = 500. Volumetric airflow (ft³/min) = 1000.

Before you use the result

Use average velocity across the section, not a single unrepresentative point. This is a flow relation, not room ventilation, pressure-drop or HVAC equipment sizing.

Example results for duct cross-section area (ft²)

These examples use Average air velocity (ft/min): 500. They are reference calculations, not recommended settings.

Duct cross-section area (ft²)	Volumetric airflow (ft³/min)
1	500
2	1000
4	2000

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