All calculators

Every duct tool and reference table on the site. Start typing to filter by name, keyword or category — search for a shape, a standard, or the thing you are trying to work out.

Duct Sizing

Duct Fitting Loss CalculatorElbow, tee and damper losses from loss coefficients, plus the straight run.

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 and velocity duct sizing, with every intermediate value shown.

Rectangular to Round Duct ConverterHuebscher equivalent diameter, both directions, with aspect ratio checks.

Duct Charts

Duct Size Chart (CFM)CFM to duct size at standard friction rates, round and rectangular.

Duct Velocity ChartRecommended velocities by application for mains, branches and outlets.

SMACNA Duct Gauge ChartGauge by pressure class and duct size, with thickness in mm and inches.

Standard Round Duct SizesEN 1506 metric and imperial spiral diameters with area and flow range.