BlueCollarDuct area
Rectangular duct area = width × height; round duct area = πD² ÷ 4.
SHEET METAL WORKERS
Sheet Metal
Duct, bend and fabrication math. Use the tabs below to switch between working calculators and quick field-reference material.
Sheet Metal
Bend Allowance
Estimate bend allowance and flat length for a simple sheet-metal bend.
Open calculator → Sheet MetalDuct Area
Calculate rectangular duct area, perimeter, and equivalent round diameter.
Open calculator → Sheet MetalRoof Panel Count
Estimate roof or wall metal panel count from coverage width and run length.
Open calculator →Field-reference aid. Use approved drawings, current codes/standards, manufacturer data and job-specific procedures for final decisions—especially for lifting, electrical, pressure, fire-protection and life-safety work.
Equivalent sizes
Equivalent-round and friction calculations are design aids; final duct sizing depends on system design and pressure loss.
Gauge warning
Gauge thickness is material-specific; the same gauge number does not mean the same thickness for every metal.
Fabrication
Bend allowance depends on material, thickness, bend radius and K-factor/tooling.
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