HVAC Duct Calculator

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HVAC Duct Calculator

Use Our Ductulator to Calculate Proper HVAC Ductwork Sizing

Duct Type

Size by

Friction Loss rate (per 100 ft in/wg)

Velocity (FPM)

CFM (Optional – leave blank to calculate duct size only)

# of 45° Bends

# of 90° Bends

# of 180° Bends

Duct TEL (Total Effective Length)
* include fittings in the Duct TEL

Duct Shape

Diameter (inches)

Width (inches)

Height (inches)

Duct Conversion Tools

Convert Rectangular Duct to Round Equivalent

Side 1 (inches)

Side 2 (inches)

Round Equivalent: – inches

Convert Round Duct to Rectangular Equivalent

Diameter (inches)

Fixed Side (inches)

Other Side: – inches

Disclaimer Statement

*Estimated in good faith, the duct size calculator is meant solely for generic, informative purposes. We do not guarantee the accuracy of this information. Please note that other external factors may affect or falsify the recommendations of this tool. For accurate values, consult a licensed heating and air conditioning professional or building engineer.

HVAC Duct Calculator