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The data is based on standard air 0.075 pounds per cubic foot density.
Friction loss (pressure drop) is in units of inches of water gauge per 100 feet of length.
FPM is velocity in flex duct, feet per minute.
CFM is flow rate in flex duct, cubic feet per minute.

Data is based on straight runs of Quietflex non-metallic flexible air ducts as tested in accordance with the Air Diffusion Council FD-72R1 test code and in accordance with ASHRAE 120-1999 "method of testing to determine flow resistance of HVAC ducts and fittings" Intertek report No. 3131865CRT-001.

This calculator is intended for use with all Quietflex flexible ducts. The calculator assumes the duct is installed in the uncompressed condition. Minimum friction loss will only be obtained when the duct is properly installed. For installation instructions refer to the duct package. Further instructions on the installation of flexible air ducts may be found in the air diffusion council's booklet "flexible duct performance and installation standards".