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 Fitting Loss CalculatorElbow, tee and damper losses from loss coefficients, plus the straight run.Duct Velocity CalculatorAir velocity from flow and duct size — or airflow from velocity — with the band flagged.Duct Weight CalculatorSheet metal weight and surface area per metre and for the whole run.DuctulatorEqual friction and velocity duct sizing, with every intermediate value shown.Fabric Duct CalculatorNewMinimum fabric duct diameter from airflow and allowable inlet velocity.Flex Duct CalculatorNewFlex duct friction with a measured compression correction, sized as installed.Kitchen Exhaust Duct CalculatorNewGrease duct size from hood airflow, checked against the velocity window.Rectangular to Round Duct ConverterHuebscher equivalent diameter, both directions, with aspect ratio checks.