Duct Sizing Calculators
Sizing duct is a trade between first cost and fan energy, and the method you pick decides which way that trade falls. These tools run the ASHRAE Chapter 21 equations directly rather than reading a chart: Darcy-Weisbach friction, the Altshul-Tsal friction factor, and air density computed from the temperature and elevation you are actually designing for. Each one shows its working, so an answer can be checked line by line before it reaches a drawing.
Duct Velocity CalculatorAir velocity from flow and duct size, with the recommended band flagged.Duct Weight CalculatorSheet metal weight and surface area per metre and for the whole run.DuctulatorEqual friction, velocity and static regain duct sizing with full workings.Rectangular to Round Duct ConverterHuebscher equivalent diameter, both directions, with aspect ratio checks.