How many cfm in a 6 inch round duct?

The airflow in a 6-inch round duct typically ranges from about 100 to 150 cubic feet per minute (CFM), depending on factors like air velocity and system pressure. A general rule of thumb is to estimate around 100 CFM for each 6-inch duct, assuming standard conditions and a moderate airflow velocity. However, the exact CFM can vary based on specific system design and application. For precise calculations, it's best to refer to engineering guidelines or use duct airflow calculators.