The calculation, without hidden assumptions
Estimate straight HVAC duct sheet-metal mass from developed perimeter, thickness and material density. Switch between rectangular and round duct, metric and imperial dimensions, then expose fabrication allowance and supplier kg/m separately instead of hiding them inside the base formula.
How to use this calculator
Choose rectangular or round duct and enter the finished straight-duct dimensions.
Enter nominal sheet thickness and material density; use project/supplier values when known.
Enter straight length and physical quantity in metres or feet.
Add an explicit fabrication allowance only when your estimating convention calls for seams, flanges or reinforcement.
Compare the geometric kg/m with supplier/fabricator kg/m before lifting, support or procurement decisions.
Where people use it
- •HVAC duct fabrication takeoff and freight estimates.
- •Compare rectangular and round straight-duct material mass.
- •Estimate bare sheet-metal line load before adding insulation or services.
- •Reverse a handling target into whole equal-length straight pieces.
- •Reconcile geometric mass against a fabricator or manufacturer kg/m figure.
Example: 600 × 300 mm rectangular steel duct, 0.8 mm sheet
Perimeter = 2 × (0.6 + 0.3) = 1.8 m. Bare mass = 1.8 × 0.0008 × 7,850 = 11.304 kg/m. Ten 2 m straight pieces weigh 226.08 kg before any explicit fabrication allowance.
What the result does not assume
- •This is straight-duct sheet geometry, not a duct-sizing or airflow calculator.
- •Nominal gauge labels are not silently converted to thickness because gauge conventions and coated-sheet thicknesses vary; enter the actual project thickness.
- •Elbows, tees, transitions, end caps, dampers, access doors, hangers, insulation, cladding and sealant are excluded unless represented by your explicit allowance.
- •Seams, flanges, stiffeners and reinforcement vary by pressure class, size and fabrication system; no universal percentage is asserted.
- •Galvanized coating and manufacturing tolerances can make finished catalogue mass differ from density geometry.
- •Bare duct self-weight alone is not a support-spacing or structural-capacity design. Use project specifications and applicable duct/support standards.
Frequently asked questions
How do I calculate rectangular duct weight per metre?+
Multiply 2 × (width + height), converted to metres, by sheet thickness in metres and material density in kg/m³.
How is round duct weight calculated?+
Use π × diameter for developed circumference, then multiply by sheet thickness and density. Spiral seams and fittings can add finished mass beyond the ideal sheet model.
Does this calculator use sheet-metal gauge?+
It uses actual thickness, which avoids pretending one gauge number has a universal thickness across material and coating conventions.
Should I add 15% for seams and flanges?+
Only if that is defensible for your fabrication/specification. MAXScanner exposes an editable allowance rather than presenting one percentage as universal.
Why is supplier kg/m different?+
Finished duct can include seams, flanges, reinforcement, coating and manufacturing tolerances. Use the supplier/fabricator figure for final procurement when available.
Can I size duct hangers from this result?+
Not by itself. Support design also depends on insulation, fittings, accessories, service loads, support spacing, pressure class and project requirements.
Semantic next steps
Continue the calculation
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Keep the result connected to the real job
MAXScanner keeps the formula and assumptions beside the result so you can verify the number before using it in a drawing, estimate, specification, worksheet or document. Where a supplier, manufacturer, drawing or applicable standard owns a requirement, that source remains authoritative.