Square & Rectangular Tube Weight Calculator

Multiply the metal cross-section by the density chain. Section area of a square tube: A = 4 × t × (side − t), where t is wall thickness. Weight per foot: lb/ft = A × 0.4335 × density (g/cm³). Worked case — 4 × 4 × 1/4 in mild steel: A = 4 × 0.25 × 3.75 = 3.75 in², so weight = 3.75 × 0.4335 × 7.85 = 12.76 lb/ft. A 20 ft stick weighs 255 lb by the sharp-corner formula, about 244 lb as published by ASTM A500 because of rounded corners. For a total order, multiply per-foot weight by stick length and quantity.

The metric (kg/m) form used on Indian and European mill lists: kg/m = 0.645 × ρ × 4t(A − t), with A and t in millimetres... in that variant the section area 4t(A−t) comes out in mm² and the constant changes: kg/m = 4t(A−t) × 0.00785, with every dimension in mm. Check it: a 100 × 100 × 6 mm box: 4 × 6 × 94 = 2,256 mm², × 0.00785 = 17.7 kg/m — the same section as a 4 × 4 × 1/4 inch tube at 12.76 lb/ft (12.76 × 1.488 = 19.0 kg/m; the 100 mm box is slightly smaller than 4 inches, hence the difference). The US form stays: lb/ft = 0.4335 × ρ × 4t(A − t), dimensions in inches.

It depends on the wall: 11 ga (0.120 in) runs 6.34 lb/ft, 1/8 in runs 6.85, 3/16 in runs 9.87, and the workhorse 1/4 in wall runs 12.21 lb/ft on the ASTM A500 list (12.76 by the sharp-corner formula). Per 24 ft stick: 293 lb at 1/4 wall. Aluminum 6061 in the same 4 × 4 × 1/4 geometry weighs 4.40 lb/ft — carry the section across with the material dropdown instead of re-searching charts.

Corner radius. Real HSS is rolled with outside corner radii from roughly 1.5t to 3t, and each corner removes a sliver of metal: an area of (1 − π/4) × r² per corner, four times over. On a 4 × 4 × 1/4 the removal is about 4.3%, which is exactly why the published 12.21 lb/ft sits under the sharp-corner 12.76. ASTM A500 tables additionally assume a design wall of 0.93 × nominal. Budget orders on the published figure; the formula is the theoretical ceiling, 4–6% above the scale reading.

Multiply by 0.344: aluminum 6061 at 2.70 g/cm³ against mild steel at 7.85. The same 4 × 4 × 1/4 section runs 12.76 lb/ft in steel and 4.40 lb/ft in aluminum — a 20 ft stick drops from 255 lb to 88 lb. That ratio is fixed by density alone; geometry never changes it. In practice aluminum boxes run thinner walls (1/8 to 3/16) because the alloy carries stress differently, so real-world savings are usually larger still.

At the same nominal dimension and similar wall, yes — a 4 × 4 × 1/4 box weighs 12.76 lb/ft while 4-inch Sch 40 round pipe weighs 10.79: the box carries 18% more metal because its corners push material away from the neutral axis. That is also why the box wins in bending about both axes (higher moment of inertia for the same area) while the round wins in torsion and pressure. Pick square for frames and columns, round for fluid lines and rotating loads — then weigh each with its own calculator rather than porting numbers between them.

None, exactly — 1/8 in (0.125) falls between 11 ga (0.1196) and 10 ga (0.1345) on the sheet-steel gauge ladder, which is why structural tube is specified in decimals instead of gauge numbers. The ladder for reference: 16 ga = 0.0598, 14 ga = 0.0747, 12 ga = 0.1046, 10 ga = 0.1345, 8 ga = 0.1644, 7 ga = 0.1793 in. Mill lists round 0.125 to '1/8 inch wall' or, in A500 design tables, 0.116 in (0.93 × nominal). When a drawing says '16 ga tube', it means 0.0598 nominal with a 0.056 design wall.

One multiplication: lb/ft = kg/m × 0.67197, and kg/m = lb/ft × 1.48816. A 100 × 100 × 6 mm box listed at 17.7 kg/m is 17.7 × 0.67197 = 11.89 lb/ft. Everything else about the calculation stays unit-consistent: section area in mm² pairs with the 0.00785 kg/m constant, area in in² pairs with 0.4335 lb/ft. Mixing the two — an inch section with the metric constant — is the classic factor-of-4.8 error.