ToolsDuct Sizing Calculator
Duct Sizing Calculator (Ductulator)
Calculate round and rectangular duct sizes based on CFM and velocity requirements.
400 (Quiet)700 FPM1500 (Commercial)
Typical: 0.08 residential, 0.10 commercial
Recommended Sizes
Enter CFM to calculate duct size.
Quick Reference: Standard Round Duct Sizes
| Diameter | CFM @ 700 FPM | CFM @ 900 FPM |
|---|---|---|
| 6" | 137 CFM | 177 CFM |
| 8" | 244 CFM | 314 CFM |
| 10" | 382 CFM | 491 CFM |
| 12" | 550 CFM | 707 CFM |
| 14" | 748 CFM | 962 CFM |
| 16" | 977 CFM | 1257 CFM |
| 18" | 1237 CFM | 1590 CFM |
| 20" | 1527 CFM | 1963 CFM |