Duct Calculator FAQ

Summary

The Duct Calculator App has been designed to provide quick, accurate sizing information for existing ducts and what-if scenarios.

Usage

Locking Dimensions:

• The lock symbols to the right of the duct dimensions indicate if
  that particular dimension is locked when calculating new equivalent
  values when a dimension is updated.
• The Diameter can be locked or unlocked.
• The Width or Height can be locked, but not both.

Using the Sliders:

• Move the sliders for Airflow, Duct Diameter, Width and Height up
  and down to match the desired duct size to calculate velocity and
  pressure drop for.
• The Diameter, Width and Height will change such that the
  equivalent size is shown:
  • Changing the diameter will updated either the equivalent Width
    or the Height, depending on which dimension is unlocked.
  • Changing the Width or Height will update the equivalent
    Diameter if it is unlocked, or the other rectangular duct dimension of
    the Diameter size is locked.

Direct Entry:

• The values for Airflow, Diameter, Width and Height can be
  directly edited in the text boxes to allow quick entry of exact numbers.
• Invalid entries will generate an error message, and must be
  corrected prior to the calculations updating.

Output:

• The values for the calculated Velocity for Round Duct and
  Rectangular Duct are shown, as is the Pressure Drop per Length value.

Assumptions

• Sheet metal ductwork, with an absolute roughness of 0.0003 ft
  (0.00762 mm).
• Air at standard temperature and pressure.