The duct calculator is an accurate, easy-to-use calculating device that aids in the layout of air handling systems, sizing of ducts and the checking of existing duct systems. With single setting, the answer to any duct sizing problem may be read directly from the face of the Ductulator. conversion of units, English-to-metric, or vice versa, is accomplished by setting up a problem on the scales of one unit system, reversing sides of the Ductulator, and reading the converted values from the scales of the other unit system.