Size round or rectangular ducts from CFM and target velocity. Converts between shapes using equivalent diameter. Pass/fail against SMACNA limits.
| Application | Recommended (FPM) | Max (FPM) |
|---|---|---|
| Supply air — main trunk | 600–1200 | 1500 |
| Supply air — branch duct | 400–800 | 1000 |
| Return air — main trunk | 500–800 | 1000 |
| Return air — branch duct | 300–600 | 800 |
| Exhaust / relief | 500–1000 | 1500 |
| Aspect ratio (max) | ≤4:1 preferred; 8:1 absolute max | |
This calculator handles one step. AIM Works runs the complete MEP design workflow — thermal load calculations, duct & pipe networks, equipment selection, code compliance, and an AI design assistant — in one tool.