HVAC Duct Sizing Calculator (Ductulator)

Equal-friction method · Round & rectangular · Velocity check · PDF + CSV

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Want a client-ready quote instead of just the numbers? Excel + Google Sheets workbook with a refrigerant compatibility check.

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Shop HVAC & Duct Tools

Genuine airflow and sheet-metal tools from the affiliate catalog — anemometer and manometer for field checks, snips and TurboShear for fabricating duct. No physical Ductulator wheel or mastic/foil-tape SKUs were in the CSV at publish time, so those are omitted rather than substituted with unrelated welding gear.

Fieldpiece STA2 In-Duct Hot Wire Anemometer

Fieldpiece STA2 In-Duct Anemometer

Hot-wire anemometer for in-duct velocity checks — confirm the FPM your sized run is actually moving.

View on Amazon →

Testo 512-2 Differential Pressure Manometer

Testo 512-2 Manometer

Differential pressure manometer for static pressure and friction-rate field checks on duct systems.

View on Amazon →

Malco M2006 Left Offset Snips

10" left-offset aviation snips for cutting galvanized duct and sheet-metal fittings in the field.

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Malco TS1 TurboShear

Drill-powered sheet-metal shear attachment for long straight cuts in galvanized duct stock.

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As an Amazon Associate, TestTalkHQ earns from qualifying purchases. No Ductulator wheel, mastic, or foil tape appeared in the affiliate CSV at publish time.

Sizing Only — What This Tool Does Not Do

It does not calculate required room CFM — that comes from ACCA Manual J (loads) and Manual D (duct design). It sizes straight runs only and does not add fitting losses (elbows, takeoffs, transitions). Calculated diameters often land between stock increments; the tool suggests the next standard size up so you never undersize airflow. Read the full guide or troubleshooting.

Companion Reading

Learn the equal-friction method in the Duct Sizing Guide. Fix no-solution and velocity-flag issues in troubleshooting. Decide shape with Round vs Rectangular Duct.

HVAC Duct Sizing Calculator (Ductulator)