Rectangular Tube Weight
A steel 80×40×4 mm rectangular tube weighs about 7.03 kg/m (4.73 lb/ft). Change the size, material or length below for an exact figure.
Common rectangular tube sizes — steel weight
| Size (mm) | kg/m | lb/ft |
|---|---|---|
| 40×20×2 mm | 1.76 | 1.18 |
| 50×30×3 mm | 3.49 | 2.34 |
| 60×40×3 mm | 4.43 | 2.98 |
| 80×40×4 mm | 7.03 | 4.73 |
| 100×50×4 mm | 8.92 | 5.99 |
| 120×60×5 mm | 13.3 | 8.97 |
Carbon steel, ρ = 7.85 g/cm³. Other materials scale linearly with density — use the selector above.
How rectangular tube weight is calculated
Weight comes straight from geometry and density: work out the cross-section area of the profile, then multiply by length and the material's density. For rectangular tube the cross-section follows rectangular tube geometry, and mass per metre is that area times density. Carbon steel is 7.85 g/cm³; that single number is why a steel part weighs almost three times an identical aluminium one (2.70 g/cm³).
The quick-reference table above is calculated for carbon steel. For any other material, use the calculator's material selector — the weight scales linearly with density, so stainless (8.0) comes out about 2% heavier than steel, and aluminium about 66% lighter, for the same dimensions.
Per-metre vs. total weight
Bar, tube and section stock is usually quoted in kg per metre (or lb per foot). The calculator shows both the per-metre rate and the total for the cut length you enter — handy for working out shipping weight or checking a delivery against the packing list.
Why calculated beats a printed chart
Stock charts only list round-number sizes in one material. Real jobs use odd cut lengths, mixed materials and non-standard sections. Computing the weight from dimensions means you get the exact figure for your piece — not the nearest row on a wall chart.
References
- Densities: standard handbook values (ASM Metals Reference Book; matweb typical values). Mill stock varies a few percent with alloy and tolerance.
- Cross-section relations: standard mensuration formulas per profile geometry.
Last reviewed: 2026-07 · Calculation method & assumptions