Air Duct Calculator
Calculate proper air duct sizes based on CFM requirements and air velocity. Get duct dimensions and material estimates.
Duct Requirements
Duct Shape:
400 CFM
50 CFM2,000 CFM
CFM
600 FPM
300 FPM1,500 FPM
Recommended: 600-900 FPM for main ducts
50 ft
10 ft200 ft
Recommended Duct Size
12" diameter
Calculated: 11.1" diameter
📐Required Area
96.0 sq in
💨Actual Velocity
600 FPM
📊Pressure Drop
1.218" WC/100ft
📏Surface Area
144.7 sq ft
Material Estimates:
Sheet Metal (with waste)159.2 sq ft
Insulation166.4 sq ft
Duct Sizing Guide
Main Supply Ducts
600-900 FPM velocity
Branch Ducts
600-700 FPM velocity
Return Ducts
400-600 FPM velocity
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Editorial Note
MyCalcBuddy Editorial Team
This page is maintained as an educational calculator reference.
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Formula Source: Standard Mathematical References
by Various
🔄Last reviewed: May 2026
✓Formula checks are based on standard references and internal QA review.