Rectangular Hollow Section Properties, Capacity & Cost Tool – Updated 2026
Select an RHS size, enter the loading and span, and this tool calculates key section properties, bending capacity (major axis), axial compression capacity, and 2026 supply cost. Based on BS EN 10219 cold-formed and BS EN 10210 hot-finished RHS sections.
The table below lists section properties for commonly specified RHS sizes in the UK, derived from BS EN 10219 (cold-formed) and BS EN 10210 (hot-finished). Values shown are for nominal dimensions; actual dimensions and tolerances are given in the relevant standard.
| RHS Size (mm) | t (mm) | A (cm²) | kg/m | Iy (cm⁴) | Iz (cm⁴) | Wel,y (cm³) | Wpl,y (cm³) | iy (cm) | iz (cm) |
|---|---|---|---|---|---|---|---|---|---|
| 50×30 | 3.0 | 4.42 | 3.47 | 17.0 | 7.10 | 6.80 | 8.60 | 1.96 | 1.27 |
| 50×50 | 3.0 | 5.42 | 4.25 | 23.5 | 23.5 | 9.40 | 11.4 | 2.08 | 2.08 |
| 60×40 | 4.0 | 7.10 | 5.57 | 37.9 | 19.3 | 12.6 | 15.6 | 2.31 | 1.65 |
| 80×40 | 4.0 | 8.52 | 6.69 | 74.4 | 22.8 | 18.6 | 23.8 | 2.96 | 1.64 |
| 80×80 | 5.0 | 14.4 | 11.3 | 102 | 102 | 25.4 | 31.0 | 2.66 | 2.66 |
| 100×50 | 5.0 | 13.5 | 10.6 | 162 | 53.0 | 32.4 | 40.6 | 3.46 | 1.98 |
| 100×100 | 5.0 | 18.4 | 14.4 | 224 | 224 | 44.8 | 54.5 | 3.49 | 3.49 |
| 100×100 | 6.0 | 21.8 | 17.1 | 261 | 261 | 52.2 | 63.8 | 3.46 | 3.46 |
| 120×60 | 5.0 | 16.4 | 12.9 | 272 | 88.1 | 45.3 | 57.0 | 4.07 | 2.32 |
| 120×80 | 5.0 | 18.4 | 14.4 | 320 | 163 | 53.4 | 66.0 | 4.17 | 2.98 |
| 120×120 | 6.0 | 26.6 | 20.9 | 467 | 467 | 77.9 | 95.2 | 4.19 | 4.19 |
| 150×100 | 5.0 | 23.4 | 18.4 | 624 | 309 | 83.2 | 103 | 5.16 | 3.63 |
| 150×150 | 6.0 | 33.4 | 26.2 | 843 | 843 | 112 | 138 | 5.02 | 5.02 |
| 150×150 | 8.0 | 43.7 | 34.3 | 1,081 | 1,081 | 144 | 179 | 4.97 | 4.97 |
| 200×100 | 6.0 | 34.6 | 27.2 | 1,504 | 448 | 150 | 188 | 6.59 | 3.60 |
| 200×100 | 8.0 | 45.3 | 35.6 | 1,919 | 566 | 192 | 242 | 6.51 | 3.54 |
| 200×200 | 8.0 | 60.9 | 47.8 | 3,204 | 3,204 | 320 | 394 | 7.25 | 7.25 |
| 200×200 | 10.0 | 75.3 | 59.1 | 3,872 | 3,872 | 387 | 479 | 7.17 | 7.17 |
| 250×150 | 8.0 | 60.9 | 47.8 | 5,034 | 2,059 | 403 | 498 | 9.09 | 5.82 |
| 250×250 | 10.0 | 95.3 | 74.8 | 7,925 | 7,925 | 634 | 782 | 9.12 | 9.12 |
| 300×200 | 10.0 | 95.3 | 74.8 | 11,440 | 5,634 | 763 | 944 | 10.96 | 7.69 |
| 300×300 | 10.0 | 115 | 90.4 | 16,500 | 16,500 | 1,100 | 1,355 | 11.98 | 11.98 |
| 400×200 | 10.0 | 115 | 90.4 | 26,050 | 7,285 | 1,303 | 1,619 | 15.05 | 7.96 |
| 400×400 | 12.0 | 183 | 144 | 62,450 | 62,450 | 3,123 | 3,836 | 18.47 | 18.47 |
Properties are calculated from nominal dimensions. For detailed design, use published tables from BS EN 10219-2 (cold-formed) or BS EN 10210-2 (hot-finished) which include additional properties (torsional constant, warping constant) and tolerances. Where properties for a specific size are not shown, interpolate between similar sizes or consult the manufacturer’s datasheet.
Indicative 2026 supply-only prices for cold-formed S275 RHS delivered to a UK construction site. Hot-finished (HF) sections carry a premium of approximately 10–20% over cold-formed equivalents. S355 grade carries approximately 5–10% premium over S275. Prices exclude fabrication, cutting, welding, surface treatment, and VAT.
| RHS Size | t (mm) | kg/m | N Ireland / Scotland | North / Wales | Midlands / SW | South East | Greater London |
|---|---|---|---|---|---|---|---|
| 50×50 | 3.0 | 4.25 | £5–£7/m | £5–£8/m | £6–£8/m | £6–£9/m | £7–£11/m |
| 80×40 | 4.0 | 6.69 | £7–£10/m | £8–£11/m | £8–£12/m | £9–£13/m | £11–£15/m |
| 100×50 | 5.0 | 10.6 | £11–£15/m | £12–£17/m | £13–£18/m | £14–£20/m | £17–£23/m |
| 100×100 | 5.0 | 14.4 | £14–£19/m | £15–£21/m | £16–£22/m | £18–£25/m | £21–£29/m |
| 120×80 | 5.0 | 14.4 | £14–£19/m | £15–£21/m | £16–£22/m | £18–£25/m | £21–£29/m |
| 150×150 | 6.0 | 26.2 | £25–£34/m | £27–£37/m | £29–£39/m | £32–£44/m | £37–£51/m |
| 200×100 | 6.0 | 27.2 | £26–£35/m | £28–£38/m | £30–£41/m | £33–£46/m | £38–£53/m |
| 200×200 | 8.0 | 47.8 | £46–£63/m | £49–£68/m | £52–£72/m | £58–£80/m | £67–£93/m |
| 250×250 | 10.0 | 74.8 | £72–£99/m | £77–£106/m | £82–£113/m | £92–£126/m | £106–£146/m |
| 300×300 | 10.0 | 90.4 | £87–£120/m | £93–£128/m | £99–£136/m | £111–£153/m | £128–£176/m |
| 400×400 | 12.0 | 144 | £139–£191/m | £149–£205/m | £159–£218/m | £178–£245/m | £205–£282/m |
A Rectangular Hollow Section (RHS) is a closed steel structural section with a rectangular or square cross-section profile and uniform wall thickness on all four sides, manufactured by cold-forming or hot-finishing steel strip into a hollow tube and welding the seam. RHS sections are manufactured to BS EN 10219 (cold-formed hollow structural sections) and BS EN 10210 (hot-finished hollow structural sections) and are available in a very wide range of sizes — from 50×30mm to 400×400mm and beyond — in wall thicknesses from 2mm to 20mm or more.
In UK structural engineering in 2026, RHS sections are used extensively for:
RHS sections are produced by two main manufacturing routes that result in different material and geometric properties:
RHS steel section resources: Steel Construction Info (SCI) | BCSA | BSI – BS EN 10219 / 10210 | Institution of Structural Engineers
RHS (Rectangular Hollow Section) has a rectangular cross-section. When H = B it is a Square Hollow Section (SHS), which has equal properties about both axes. A Circular Hollow Section (CHS) is round and has the most efficient torsional performance but more complex connections. All three are “hollow sections” or “structural hollow sections (SHS)” — RHS and SHS are subcategories.
A key advantage of RHS over open sections (UB, UC, angle) is their very high torsional stiffness. The closed cross-section has a torsional constant J many times greater than an equivalent open section, making RHS much more resistant to twisting under eccentric loads. This makes them ideal for members subject to combined bending, torsion, and axial forces.
For RHS beams, lateral torsional buckling (LTB) is generally not a governing failure mode because the closed section has very high torsional stiffness. In most practical cases, the full plastic moment resistance Mpl,Rd can be achieved without LTB reduction — a significant advantage over open sections such as UBs, which require LTB checks for most span conditions. Always verify this assumption for very long, lightly restrained spans.
Under EC3 Table 6.2: Hot-Finished (HF) RHS columns use buckling curve a (α=0.21) for both axes — the most favourable curve, reflecting low residual stresses. Cold-Formed (CF) RHS columns use buckling curve c (α=0.49) for both axes — significantly less favourable, reflecting higher cold-forming residual stresses. This is a major design difference — a CF RHS column has noticeably lower buckling resistance than an equivalent HF section of the same size and steel grade.
RHS sections are classified under EC3 Table 5.2 by the slenderness of the web and flange in compression. For an RHS in bending, the web slenderness hw/t is checked against the class limits (Class 1: ≤ 72ε, Class 2: ≤ 83ε, Class 3: ≤ 124ε). Standard RHS sizes in S275 are almost always Class 1 or Class 2 for typical wall thicknesses, allowing the full plastic section modulus Wpl to be used for moment resistance.
For structural applications, the minimum RHS wall thickness is typically 3mm for lightly loaded members and 5mm for structural columns and beams. For connections, the wall must be thick enough to accommodate welds and cope with punching shear — minimum 4mm for welded connections is a common practical rule. Very thin-walled sections (<3mm) have limited structural use and are generally confined to secondary framing and architectural applications.
RHS sections are typically supplied in 6m and 12m stock lengths from UK steel stockholders, with 7.5m available for some sizes. Custom cut lengths are available from most stockholders at a cutting surcharge. Offcuts can often be purchased at reduced cost for shorter lengths. For project orders, it is most economical to specify lengths that minimise offcuts from standard stock.
RHS sections are highly suited to welded connections — the flat faces allow full-perimeter fillet welds and CJP (complete joint penetration) welds in truss applications. Gap-welded K and N joints in hollow section trusses are designed to EC3 Part 1-8, which provides specific joint efficiency formulae based on the ratio of chord to brace wall thickness and section dimensions. Always design connections to match the RHS specification (CF or HF) as joint capacity formulae differ.
RHS sections have a smaller surface area per tonne than equivalent open sections, reducing painting and fire protection costs. The absence of internal corners and re-entrant angles makes surface preparation easier. However, the internal void of a closed section can retain moisture — either seal both ends (for external use) or allow ventilation. Hot-dip galvanised RHS requires venting holes to prevent explosive steam pressure during galvanising.
Typical UK applications by RHS size in 2026: 50–80mm: balustrade posts, handrails, light gates; 100–120mm: light structural frames, mezzanine supports, architectural features; 150×150 to 200×200mm: structural columns 3–5m height, portal frames; 250–300mm: heavily loaded columns, transfer frames; 400mm+: major structural columns, industrial frames, heavy crane supports.
RHS sections typically cost 10–25% more per tonne than equivalent UB/UC open sections due to the additional manufacturing process. However, the cost advantage of RHS — reduced fire protection area, reduced painting costs, better torsional performance, cleaner architectural appearance — often more than offsets the material premium for exposed structural applications.
RHS design involves checks beyond bending and axial capacity: shear-bending interaction (if VEd > 0.5Vc,Rd), combined bending and axial (beam-column) per EC3 Clause 6.3.3, connection design (EC3 Part 1-8), fire resistance, fatigue (for dynamic loading), and serviceability deflection. These checks require a Chartered Structural Engineer.
RHS stands for Rectangular Hollow Section — a closed steel structural section with a rectangular cross-section and uniform wall thickness on all four sides. When the height and width are equal, the section is specifically called a Square Hollow Section (SHS), though it is still a sub-type of RHS. RHS sections are manufactured to BS EN 10219 (cold-formed) or BS EN 10210 (hot-finished) and are designated by their external height × external width × wall thickness in millimetres, for example “150×150×6 RHS” (150mm × 150mm external dimensions with 6mm wall thickness).
For a rectangular hollow section with external height H, width B, and wall thickness t, the approximate section properties are: Area A ≈ 2t(H+B−2t) cm²; Iy ≈ (BH³−(B−2t)(H−2t)³)/12 cm⁴ (about major axis); Wel,y = Iy/(H/2) cm³; Wpl,y ≈ 1.13×Wel,y for typical RHS proportions; iy = √(Iy/A) cm. For precise values, use the tabulated properties in BS EN 10219-2 or BS EN 10210-2, which account for the actual corner radii. The calculator above computes these properties automatically for the selected section.
The key differences are: Manufacturing process: CF RHS (BS EN 10219) is formed at room temperature; HF RHS (BS EN 10210) is formed at elevated temperature. Residual stresses: CF sections have higher residual stresses from cold-working; HF sections have lower, more uniform residual stresses. EC3 buckling curves: CF uses curve c (α=0.49) — less favourable; HF uses curve a (α=0.21) — more favourable, giving significantly higher column resistance for the same size. Corner radii: CF sections have larger corners (≈2t); HF sections have smaller corners (≈1.5t). Cost: CF is typically 10–20% cheaper. For most UK applications where columns are not heavily loaded, CF sections are preferred for economy.
For most practical RHS beams, lateral torsional buckling (LTB) is not the governing failure mode because the closed rectangular cross-section has very high torsional stiffness. EC3 Clause 6.3.2.1 permits the buckling resistance to be taken as the full plastic moment Mpl,Rd (i.e. χLT = 1.0) for hot-finished RHS with very low slenderness, and in most cases the LTB slenderness λ̅LT is below the plateau value (typically 0.4). However, for very long, unrestrained RHS beams loaded in the weak direction or with very deep narrow sections (H/B > 2.5–3), an LTB check may be prudent. The calculator above assumes no LTB reduction (appropriate for most square and moderately proportioned RHS in typical spans).
For preliminary sizing only — a 3m pin-pin column carrying 200 kN axial load in S275 CF RHS: the non-dimensional slenderness λ̅ = (Lcr/i) / (93.9ε). For a 100×100×5 CF RHS (iz = 3.49cm): λ̅ = (3000/34.9) / (93.9×1.0) = 86.0 / 93.9 = 0.92; with buckling curve c (α=0.49): Φ = 0.5(1+0.49(0.92–0.2)+0.92²) = 1.10; χ = 1/(1.10+√(1.10²–0.92²)) = 0.57; Nb,Rd = 0.57×18.4×100×275/1000 = 288 kN > 200 kN — adequate. A 100×100×5 CF RHS in S275 would be a reasonable preliminary choice for this scenario. Always verify with a full EC3 check.
In the UK in 2026, cold-formed S275 RHS supply costs per linear metre range from approximately £5–£9/m for small sections (50×50×3) through to £178–£245/m for large sections (400×400×12) in South East England. A commonly used mid-range size — 150×150×6 RHS in S275 — costs approximately £32–£44/m in the South East. Prices are 15–20% lower in Northern England and Scotland and 15–20% higher in Greater London. Fabrication (cutting, welding, drilling, surface treatment) typically adds £800–£2,000/tonne on top of material supply cost. Always obtain at least three competitive quotes from UK steel stockholders.
Yes — RHS sections are effective as both beams and columns (and as combined beam-columns). As a beam, an RHS provides good bending resistance about the major axis and, as noted above, generally avoids lateral torsional buckling issues. For asymmetric rectangular sections (e.g. 200×100 RHS), the section is most efficient as a beam when the longer dimension (200mm) is vertical (major axis bending). Square sections (e.g. 150×150) are equally efficient in bending about either axis, which is useful in members subject to bi-axial bending. When an RHS member carries significant axial load in addition to bending — as in a portal frame rafter or inclined column — it must be designed as a beam-column per EC3 Clause 6.3.3, which requires the structural engineer to check the combined bending and axial interaction.
The appropriate surface treatment for RHS depends on the exposure environment and aesthetic requirements. Common options in UK construction in 2026 are: Shot blast and prime (SA2.5, zinc phosphate primer): standard for structural steelwork in dry interiors; typically £100–£200/tonne at the fabricator; protective topcoat applied on site or in the fabricator’s shop. Hot-dip galvanising: excellent corrosion protection for external or aggressive environments; £200–£400/tonne; note that hollow sections must have vent holes. Powder coating: for architectural finishes; wide colour range; typically £25–£60/m² applied. Intumescent paint: required for fire protection where the period of fire resistance exceeds the unprotected critical temperature; £15–£60/m² depending on the required fire period. Always specify the surface treatment in the structural specification alongside the section grade and standard.