How Do you Calculate CFMMeasure the length and width of a room where you need to calculate the required airflow.Continue measuring each room and calculating the CFM requirement for each.Add up each room’s required CFM.If you don’t already have a HVAC unit for the space, purchase one at your local HVAC retailer that matches your CFM requirement.Using your Ductulator, match each room’s CFM requirement to your planned friction rate.See More….