RETURN DUCT SIZING CALCULATOR
Penguin Air & Plumbing - Interactive Field Tool
Version 1.4
System Information
Design CFM Required
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(Based on 400 CFM per ton)
Return Ducts
Enter each return duct size and length. Runs up to 100 ft use the reference capacity. Runs over 100 ft are reduced for added friction loss.
Return Duct 1
Return Duct 2
Return Duct 3 (Optional)
Duct Sizing Reference (Flex Duct)
| Duct Size | CFM @ 100 ft | Typical Use |
|---|---|---|
| 8" | 200-300 CFM | Small returns, bedroom |
| 10" | 300-450 CFM | Medium returns |
| 12" | 450-600 CFM | Common return size |
| 14" | 600-800 CFM | Larger systems |
| 16" | 800-1100 CFM | Large returns |
| 18" | 1100-1400 CFM | Very large returns |
| 20" | 1400-1700 CFM | 5-ton systems |
| 22" | 1700-2000 CFM | Large 5-ton systems |