How much a tube or hollow section weighs

Mass per metre of a hollow section: 40×40×3 — 3.30 kg/m, 60×40×3 — 4.25 kg/m, 100×100×5 — 14.4 kg/m; of a round tube: 42.4×3.2 — 3.09 kg/m (a 6 m length is 18.6 kg). Enter your own dimensions and wall thickness — the calculator gives one piece, the whole batch and a running metre, and below are tables of the usual commercial sizes to EN 10219.

Short answer

Mass per metre of a hollow section is F · ρ / 1000, where F is the cross-sectional area in mm² and ρ = 7.85 g/cm³ for steel. For a round tube the formula shortens to m = π · t · (D − t) · 0.00785 kilograms per metre. Most asked for: section 50×50×3 — 4.25 kg/m, 80×40×4 — 6.71 kg/m, 80×80×4 — 9.22 kg/m; tube 33.7×3.2 — 2.41 kg/m, 60.3×3.6 — 5.03 kg/m, 76.1×3.6 — 6.44 kg/m.

Circular hollow section weight formula, worked through

Mass per metre of a round tube is the ring area times density: m = π · t · (D − t) · ρ / 1000, where D is the outside diameter and t the wall, both in mm, giving kg/m. For steel the constants collapse into one multiplier: m = 0.02466 · t · (D − t).

Example: 42.4×3.2 CHS.

1. D − t = 42.4 − 3.2 = 39.2 mm.
2. 0.02466 × 3.2 × 39.2 = 3.09 kg/m — the same as the table below.
3. Check it another way: bore d = D − 2t = 36.0 mm, area π/4·(42.4² − 36.0²) = 394.1 mm², times 7.85/1000 — 3.09 kg/m again.
4. A 6 m length weighs 18.6 kg; twelve lengths for a handrail run, 223 kg.

A second example, 60.3×3.6: 0.02466 × 3.6 × 56.7 = 5.03 kg/m, and 76.1×3.6 comes to 6.44 kg/m. The same tube in stainless is 1.006 times heavier (42.4×3.2 — 3.11 kg/m), in aluminium 1.06 kg/m; common aluminium tube sizes are in the aluminium tube weight calculator.

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Hollow section weight chart: square and rectangular, kg per metre

Rectangular hollow section weight: why the calculator reads higher than the table

The calculator at the top of the page treats the section as the difference of two rectangles: a·b − (a − 2t)·(b − 2t), which simplifies to 2t · (a + b − 2t). A real EN 10219 section has rounded corners: outer radius r₀ = 2t, inner r₁ = t (for walls up to 6 mm). Each of the four corners is missing a sliver of steel, together (4 − π)·(r₀² − r₁²).

Step by step for 60×40×3. Simplified: 2 · 3 · (60 + 40 − 6) = 564 mm², i.e. 4.43 kg/m. Corners: r₀ = 6, r₁ = 3, (4 − π) · (36 − 9) = 23.2 mm² to take off. That leaves 540.8 mm² and 4.25 kg/m — exactly the table.

The gap is widest on small sections with a thick wall (30×30×3 +7.8 %, 40×40×4 +7.7 %) and narrows on big ones (150×150×6 +2.8 %). Rule of thumb: orders, quotes and settling up with the stockholder go by the EN table; the calculator figure can stay where a margin does no harm — choosing a sling or checking a trolley's rating.

Round tube weight chart: kg per metre by diameter and wall

Pipe sizes in inches and DN: the actual outside diameter

Threaded and service pipe is ordered in inches or by nominal size DN, but the formula needs the outside diameter. The inch in the name is a nominal figure that matches no dimension of the pipe; the table lines both up with the tube masses from the table above.

The classic mistake is an "inch" pipe worked out at 25.4 mm. A 1″ pipe is DN25 with a 33.7 mm outside diameter; with a 3.2 mm wall it weighs 2.41 kg/m, whereas 25.4×3.2 would give 1.75 kg/m — 27 % light. The wall of such pipe depends on the series (light, medium, heavy), so take it from the order or the mill certificate before you calculate.

Cross-section formulas

In the last formula r₀ is the outer corner radius (taken as 2t for walls up to 6 mm) and r₁ = r₀ − t. Mass per metre is always F · ρ / 1000 kilograms with F in mm².

Metres per tonne and what a frame weighs

Stockholders price by the tonne, drawings are in metres. Metres per tonne is 1000 divided by mass per metre: 40×40×2 box — 433 m, 40×40×3 — 303 m, 60×40×3 — 235 m, 80×80×4 — 108 m, 42.4×3.2 tube — 324 m. In 6 m lengths a tonne of 40×40×2 is 71.9 lengths, of 60×40×3 39.2.

Example: a 3000×2000 sliding gate.

1. Frame in 60×40×3: perimeter 10 m plus two intermediate uprights of 2 m — 14 m in all.
2. 14 m × 4.25 kg/m = 59.5 kg from the EN table (the no-radius calculator shows 62.0 kg).
3. Infill in 40×20×2: 20 pieces of 1.9 m = 38 m × 1.68 kg/m = 63.8 kg.
4. About 123 kg in total before hardware, wheels and any sheet — the figure the rollers and the operator are chosen by.

Nesting those pieces into 6 m lengths with the least waste is what the cutting list optimiser does, and the bill of materials totals the whole schedule with an allowance and a price.

The same sum works for a table frame in box section or a barbecue chimney — how those pieces are built is shown under furniture and interior and barbecues and stoves.

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Common mistakes with tube and hollow section weight

• Bore instead of outside diameter. Take 42.4 as the bore and enter 48.8 as the outside, and you get 3.60 instead of 3.09 kg/m.
• An inch as 25.4 mm. A 1″ pipe is 33.7 mm outside — see the DN table above.
• Wall in the wrong unit. 3.2 mm is 0.32 cm; typed as 32 it turns the tube into a solid bar and the calculator returns nonsense.
• Dimension order. The trade notation is a×b×t with the wall last: 60×40×3, not 3×40×60.
• Calculator instead of table for tonnage. On 20 t of section a 3–8 % overstatement is 600 kg to 1.6 t of steel that will not be on the lorry.
• Stainless and aluminium at 7.85. For stainless the error is 0.6 %, for aluminium nearly threefold.

Welding hollow sections

The thin wall is the main problem: at 2 mm a burn-through is a matter of a second, and on a corner half a second, because the heat has nowhere to go. Current follows the thinnest part, not the overall size of the section: 40×40×2 is 60–80 A work with a 2.0 mm electrode, or short-arc MAG at 90–110 A with 0.8 mm wire.

The second problem is the frame pulling out of square. A closed section is stiff in torsion, but a frame built from it bows under uneven heating just like any other. Tacks go closer than on a beam — every 200–300 mm — and welding alternates: opposite sides first, then the rest.

The third is moisture and rust inside. A closed section collects condensate, and a fully sealed frame bursts from pressure the first time it is heated hard if it has no vent. In hot-dip galvanised work vent holes are mandatory; in ordinary work they are simply sensible.

Cutting and fitting sections to each other is covered in welding hollow sections; matching current to thickness in the welding current calculator.

Author: Dmitry Frolov, welder and metal fabricator Updated: 5 October 2026