Based on Friction Loss:

• Enter Friction Loss (inches of water), Duct Airflow (CFM), Duct Length  and the number of bends.
• Read Duct Diameter (inches) and Duct Velocity (FPM).

Based on Duct Diameter:

• Enter Round Duct Diameter (inches), Duct Airflow (CFM), Duct Length and the number of bends.
• Read Friction Loss (inches of water) and Duct Velocity (FPM).

Equivalent Rectangular Duct:

• Enter Round Duct Diameter.
• Enter the Desired Length of the Rectangular Duct.

Equivalent Round Duct Diameter:

• Enter the Length of the Rectangular Duct.
• Enter the Width of the Rectangular Duct.

Maximum Recommended Supply Velocity:

Foot per Minutes	Main Duct	Branch Duct
Residential	9000	600
Commercial	1300	900
Industrial	1800	1000