HVAC · Air side
A 8 in round duct carries about 212 CFM
The airflow a 8 in round duct carries at the common 0.08 in. wc per 100 ft residential friction rate, galvanized steel, standard air, before friction and noise pass the design target. Computed from the Darcy-Colebrook duct model, not looked up.
8 in duct airflow (0.08 in. wc/100 ft)
| Property | Value |
|---|---|
| Round size | 8 in |
| Max airflow at 0.08 | ~212 CFM |
| Friction target | 0.08 in. wc/100 ft |
These are static reference figures at the residential design rate. For your own airflow and friction rate, run the interactive duct size calculator, or convert a shape with the round-to-rectangular converter.
FAQs
How many CFM does a 8 inch duct carry?
A 8 in round duct carries about 212 CFM at the common 0.08 in. wc per 100 ft friction rate (galvanized steel, standard air). Push more air through it and the velocity and friction climb past the residential target, which is where duct noise starts.
Is a 8 inch duct big enough for my run?
It depends on the airflow the room needs. A 8 in round is right up to about 212 CFM at 0.08 in. wc per 100 ft; above that, step up to the next size. Enter your actual CFM in the duct size calculator to confirm.
What friction rate is this based on?
0.08 in. wc per 100 ft, the standard residential design target that ACCA Manual D Appendix 3 tables assume. A higher target lets a given duct carry more air at the cost of more velocity and noise.