Airflow reference: CFM per ton
The design rule of thumb is 400 CFM per ton of cooling (350–450 CFM/ton in practice). Use it to check supply airflow and register count with the duct-CFM and CFM-from-tonnage tools.
| Tons | CFM @ 400/ton | Range (350–450) |
|---|---|---|
| 1.5 | 600 | 525–675 CFM |
| 2.0 | 800 | 700–900 CFM |
| 2.5 | 1,000 | 875–1,125 CFM |
| 3.0 | 1,200 | 1,050–1,350 CFM |
| 3.5 | 1,400 | 1,225–1,575 CFM |
| 4.0 | 1,600 | 1,400–1,800 CFM |
| 5.0 | 2,000 | 1,750–2,250 CFM |
400 CFM/ton is the design default; humid climates sometimes target ~350 CFM/ton for more dehumidification.