Round Duct Hanger Load Calculator
Weights use a SMACNA-style baseline for galvanized spiral round duct. Results show per-hanger load.
Inputs
Results
Reference Weights (lbs/ft) — Galvanized Spiral Round (per SMACNA)
Values reflect bare duct weight. Fitting allowance is calculated separately.
| Dia (in) | 26 ga | 24 ga | 22 ga | 20 ga | 18 ga |
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Always verify weights against specific manufacturer submittals.
How to Calculate Hanger Loads for Round Spiral Duct
Estimating the weight of spiral ductwork is critical for selecting the correct suspension system. This calculator uses standard SMACNA weight baselines for galvanized steel to help you determine the total load per hanger.
Select Diameter & Gauge: Choose your duct size (4″ to 60″) and sheet metal gauge (26ga to 18ga).
Define Spacing: Enter your hanger spacing (typically 10ft or 12ft per project specs).
Add Fittings Allowance: Bare duct is light, but a run of ductwork includes heavy flanges, elbows, dampers, and stiffeners. We recommend a 15% to 20% buffer to account for these accessories.
Check Capacity: Select your cable rating (e.g., 100 lb or 200 lb). The tool will instantly flag if your spacing or duct weight exceeds the Safe Working Load (SWL) of the suspension system.
Why use Cable Suspension for Spiral Duct?
Round spiral duct is frequently installed in “open ceiling” environments where aesthetics matter (e.g., restaurants, offices, gyms). Traditional strap hangers or bulky unistrut trapezes can look cluttered.
Aesthetics: Cable suspension is nearly invisible from the ground, making the ductwork appear to float.
Speed: Loop-style cable hangers wrap around the round profile naturally, eliminating the need to cut and bend heavy steel straps.
Leveling: Cable locks allow for instant, tool-free height adjustments, making it easy to level long runs of spiral duct perfectly.
Frequently Asked Questions (Round Duct)
What is the maximum hanger spacing for round duct?
According to SMACNA standards, the maximum spacing for horizontal round duct is typically 12 feet. However, most engineers specify 10 feet to ensure stability and reduce sagging. Always check your specific project drawings.
How does the calculator determine "Base Weight"?
The calculator references a standard density table for galvanized steel spiral duct. For example, a 12-inch diameter duct at 24 gauge weighs approximately 2.4 lbs per linear foot. If you are using double-wall or insulated duct, you must account for that extra weight manually.
Should I include a safety factor?
Most engineered cable suspension systems (like Gripple or similar brands) already include a 5:1 safety factor in their rated Safe Working Load (SWL). Therefore, entering “1” in the safety factor box is standard unless your project explicitly requires an additional margin of safety.
Does this work for stainless steel or aluminum?
This calculator is calibrated for Galvanized Steel, which is the industry standard for HVAC. Stainless steel is slightly heavier, and aluminum is significantly lighter. For those materials, please consult the manufacturer’s specific weight data.
Legal Disclaimer & Usage Notice
The results provided by this calculator are for informational and estimation purposes only. While the weight models are based on standard SMACNA industry data, actual duct weights may vary depending on the specific sheet metal manufacturer, seam type, reinforcement, insulation, and liners used.
Important:
Verify Capacities: Always reference the specific cable manufacturer’s data sheets for Safe Working Loads (SWL) and safety factors.
Professional Review: These calculations do not constitute professional engineering advice. A licensed structural engineer or qualified project manager must review and sign off on all load calculations and suspension methods prior to installation.
Liability: www.cablesuspension.com assumes no liability for errors, omissions, or damages resulting from the use of this tool. It is the user’s responsibility to ensure compliance with all local building codes and project specifications.