Cfm And Duct Size Chart

Flex duct has a higher pressure drop and as such may require the size shown on this guide be increased by 1 round size for up to 800 cfm and 2 round sizes above 800 cfm to insure proper airflow.

Cfm and duct size chart.

Larger volumes or higher static pressures should be dealt with on an individual job basis. The chart is based on metal duct. Field duct sizing chart rectangular sheet metal duct 07 on most metal duct calculators duct size duct height net inside dimension in inches round duct size estimate. Step three if desired airflow exceeds the cfm rating increase to the next duct size step four listed cfm is based on typical field results and may vary install dampers step five if duct run exceeds 25 or has excessive transitions increase to the next size step six design alone is inadequate always prove design by test and balance.

Failure to do so will result in high velocity and very likely loss of airflow. Cfm 4 cfm 6 cfm 8 cfm 10 cfm 12 60 6x4 60 4x6 90 4x8 120 4x10 150 4x12 90 8x4 110 6x6 160 6x8 215 6x10 270 6x12. This equal friction method of duct sizing should be adequate for normal residential furnace heating and air conditioning applications. Air volume equivalent round air volume cfm 4 6 8 10 12 duct inches cfm 50 6 x 4 550 75 6 x 4 675 100 8 x 4 6 x 6 6 100 125 10 x 4 6 x 6 7 125.