How much air can 14x20 duct carry?

The amount of air a 14x20 duct can carry depends on various factors, including the velocity of the air and the duct's design. However, a rough estimate suggests that a 14x20 inch duct can carry approximately 1,200 to 1,500 cubic feet per minute (CFM) at typical airflow velocities. For precise calculations, it's important to consider factors like friction loss and the overall HVAC system design.