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Calculate duct diameter and rectangular dimensions from CFM airflow requirements.
HVAC duct sizing determines the correct duct dimensions based on airflow (CFM) requirements to ensure proper air distribution, comfort, and energy efficiency.
Residential: 600โ900 FPM. Commercial: 1000โ1500 FPM.
Equivalent Rectangular Options
| Room | CFM Range |
|---|---|
| Bedroom (150 sq ft) | 75โ100 |
| Living Room (300 sq ft) | 150โ200 |
| Kitchen (200 sq ft) | 100โ150 |
| Bathroom (75 sq ft) | 50โ75 |
| Home Office (120 sq ft) | 60โ90 |
| Master Bedroom (250 sq ft) | 125โ175 |
| Dining Room (180 sq ft) | 90โ120 |
Formula
Duct Area (sq in) = (CFM รท Velocity) ร 144CFM = Required airflow in cubic feet per minute
Velocity = Air speed in feet per minute (FPM)
144 = Conversion factor from sq ft to sq inches
Worked Example
150 CFM at 700 FPM velocity
Did you know? The average U.S. home loses 20-30% of conditioned air through leaky ductwork, according to ENERGY STAR โ proper duct sizing and sealing can significantly reduce energy waste.
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