Estimate rectangular or round sheet-metal duct mass from mean dimensions, length, thickness and material density. Optional overrides, an explicit extra mass allowance and a USD-per-pound price are available.

Straight sheet-metal duct estimate using mean sheet dimensions. Ends, fittings, insulation and supports are excluded; enter any extra allowance explicitly.

Illustrative densities; use a supplier density override for your exact grade/coating.

Gauge systems differ by material. Enter measured thickness below for another specification.

Optional settings

Blank uses the selected nominal preset.

Blank uses the approximate selected material density.

Blank means 0%. No standard allowance is assumed.

Blank omits cost; zero means no material charge.

Duct Weight Formula

The following thin-wall formula estimates a rectangular duct shell using mean sheet dimensions; use consistent inch and pound units. Ends, fittings, insulation and supports are excluded.

DW = ((2 × (H + W)) × L × T) × D

Variables:

  • DW is the Duct Weight (lbs)
  • H is the duct height (in) 
  • W is the duct width (in) 
  • L is the duct length (in) 
  • T is the duct thickness (in)
  • D is the duct density (lbs/in^3)
    • The approximate aluminum default is 0.0975 lb/in³. Use a supplier density for the specific alloy; the example below uses a custom 0.1 lb/in³ assumption.

For a rectangular shell, multiply 2(H + W) by length, thickness and density. For a round shell, replace 2(H + W) with π times the mean diameter. Multiply bare shell mass by (1 + allowance/100) only when an extra mass allowance is entered; blank means 0%. Nominal gauge presets are galvanized-steel thicknesses and do not specify the same gauge for other materials.

How to Calculate Duct Weight?

The following example outlines the calculation with a measured thickness of 0.25 in, custom density of 0.1 lb/in³ and no extra mass allowance. Enter the 200 in length using the length unit selector.

Example Problem #1

  1. First, determine the duct height (in).
    • The duct height (in) is calculated to be 10.
  2. Next, determine the duct width (in).
    • The duct width (in) is measured to be 15.
  3. Next, determine the duct length (in).
    • The duct length (in) is found to be 200.
  4. Next, determine the duct thickness (in).
    • In this case the thickness is .25 inches.
  5. Finally, calculate the Duct Weight using the formula above: 

DW = ((2*(H+W))*L*T)*D

The values provided above are inserted into the equation below and computed.

DW = ((2*(10+15))*200*.25)*.1 = 250.00 (lbs)