MachineCalcs

Rectangular Tube Weight Formula

Rectangular tube weight is density times the hollow rectangle area. Subtract the inside rectangle (w - 2t)(h - 2t) from the outside rectangle w*h, then multiply by length.

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Rectangular tube formula

For rectangular tube, subtract the inside hollow rectangle from the outside rectangle. If w is outside width, h is outside height and t is wall thickness, the metal area is: A = w * h - (w - 2t)(h - 2t) Then weight (kg) = rho * A * L / 1,000,000.

For mild steel, rho = 7.85 g/cm3, so kg/m = 7.85 * A / 1000 when A is in mm2.

Worked example: 80 x 40 x 3 steel tube

An 80 x 40 x 3 mm rectangular steel tube has inside dimensions 74 x 34 mm. Area is 80 * 40 - 74 * 34 = 684 mm2. Weight per metre is 7.85 * 684 / 1000 = 5.37 kg/m, so a 6 m length weighs about 32.2 kg.

RHS, HSS and mechanical tube

Rectangular hollow section (RHS), rectangular HSS and mechanical rectangular tube use the same area calculation once the outside dimensions and wall thickness are known. Published structural-section tables include corner radii and tolerances, so use those tables for final structural design weights.

Changing material

The area calculation does not change between steel, stainless and aluminum tube. Only the density changes, so an aluminum rectangular tube of the same size weighs about one third as much as a mild-steel tube.

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Last reviewed: June 1, 2026.