Extruded aluminium I-beams run from 50 × 30 mm to about 300 × 150 mm, from 0.99 kg/m to 15.68 kg/m, with a strong-axis moment of inertia of 15 to 8,871 cm⁴ and a section modulus of 5.8 to 591 cm³. Every size is a die, not a stock item, so the tables below are calculated from nominal geometry at 2.70 g/cm³ and can be checked line by line before you order.

Why there is no standard aluminium I-beam size chart

A rolled steel shape comes off a mill in a fixed set of sizes, which is why IPE and W-shape tables exist and everyone designs from them. An extruded section is the inside of a die, and the die is cut to a drawing. Depth and flange width are limited by the press and by how the metal flows; wall thickness is limited at the thin end by push speed and at the thick end by how slowly the core cools. On presses from 500 MT to 5,000 MT our practical envelope is a depth of about 300 mm, a flange width of about 200 mm, a wall from 0.8 mm, inside a 540 mm circumscribed circle. Past roughly 300 mm depth the web cools slower than the flanges, the differential contraction pulls the section into a twist, and straightening costs more than the extra depth is worth. If a design needs 400 mm, the answer is usually two shallower sections joined, not a bigger die.

Section properties of four reference beams

Strong axis, square corners, root radii ignored, density 2.70 g/cm³. The figures are geometry, not a stock list: the certified mass travels on the mill test certificate, and the numbers move once your drawing fixes the fillets and the taper. Going from 100 mm to 200 mm depth multiplies the weight by 3.2 and the moment of inertia by 13.4, so stiffness per kilogram rises from 59 to 248 cm⁴ per kg/m.

What load each size carries at L/250

Uniformly distributed load on a simply supported beam, deflection capped at L/250. Worked example: a 200 × 100 beam spanning 4 m under 3 kN/m — 1.2 t spread over the span — deflects 6.8 mm and develops 28 MPa, about 12% of the 6061-T6 yield strength. Read the last column: at the load where the structure already feels too springy, no section here has used even 60% of the alloy's strength.

Why a stronger temper does not make the beam stiffer

6061-T6 and 6063-T5 share the same modulus, 69 GPa. Temper changes yield strength, not stiffness: 6063-T5 gives 110 MPa minimum yield, 6061-T6 gives 240 to 245 MPa depending on whether you read GB/T 5237 or ASTM B221. In a beam whose load is set by deflection — per the table above, most of them — that difference buys nothing. It buys something where stress is actually being called on: spans short enough to run above 60% of yield, concentrated loads, bolt bearing at connections, machined or threaded features, and parts that take an impact.

Flange, web and taper: where the stiffness comes from

Taking the 200 × 100 flange from 10 mm to 12 mm adds 11.9% to the weight and 13.9% to Ix. Taking the web from 6.5 mm to 8 mm adds 8.5% to the weight and only 3.4% to Ix. Flange thickness buys bending stiffness; web thickness buys shear capacity and very little else. A tapered flange concentrates the extra material at the root, where the flange-to-web fillet carries the highest stress, and keeps the toe thin where there is little to carry. A 0.5–1 mm radius at an internal corner costs nothing in section properties and removes most of the stress concentration a sharp corner creates.

Weight tolerance, cutting list and container loads

Weight is calculated from the drawing and confirmed on the certificate; against that theoretical figure we work to a ±10% weight tolerance, which matters if you buy by the tonne — ask which weight is invoiced before comparing two suppliers on price per kilogram. There is no standard length: sections are cut to your cutting list, and the cutting list sets the packing. A 20 ft container takes up to 5.85 m, a 40 ft takes 6.0 m in two lengths because the internal length is about 12 m; below 5 m, sawing is charged separately. Minimum order is 500 kg whether or not a new die is cut. On a route that allows 24 t of cargo, 24,000 kg of 200 × 100 is about 2,800 m, and the same tonnage in 300 × 150 is about 1,530 m.

What to send with the enquiry

1. Section drawing — DWG, DXF or PDF, with overall depth and width, wall thicknesses, corner radii and any taper.
2. The span, the load and the deflection limit you are designing to.
3. Alloy and temper, or the duty the part does if you have not fixed them.
4. Finish and whether it is a visible face.
5. Total metres and the cutting list, so packing can be quoted with the price.
6. Destination port.

What these tables do not cover

They are elastic checks on nominal geometry, not a structural certification. They ignore root radii, local buckling of a thin web in compression, concentrated loads, torsion, fatigue and the connection, which is where aluminium frames usually fail. A welded joint loses temper in the heat-affected zone and drops to roughly T4 strength there, so a section designed as T6 at the weld is designed wrong. The design is signed off by your engineer of record; if these numbers get you close to a decision, send the drawing and we will check the geometry against the die and the press before you commit.

Where these sections are used

Machine bases and gantries, conveyor and crane rails, mezzanine framing, panel stiffeners, truck and trailer crossmembers, and architectural reveals. The heavier structural duty and the welding questions are worked through on our extruded aluminium I-beam and T-profile page; the tolerance grades behind these tables are set out under aluminium extrusion tolerances.