Aluminium angle weight calculator
Angle in aluminium alloy: 9 common sizes with the mass per metre, and a calculator for your own. Aluminium weighs under 35 % of the steel of the same section.
Short answer
The mass of aluminium angle is the cross-section area times 2.70 g/cm³: a 30×30×3 mm angle weighs 0.462 kg/m, 40×40×3 mm weighs 0.624 kg/m and 50×50×5 mm weighs 1.28 kg/m. A 6 m length of 40×40×3 mm is therefore about 3.74 kg. Aluminium weighs under 35 % of steel angle of the same section. The masses of common sizes are in the table below.
Common sizes and mass per metre
| Size, mm | Cross-section, mm² | kg/m |
|---|---|---|
| 15×15×2 | 56 | 0.15 |
| 20×20×2 | 76 | 0.21 |
| 25×25×2 | 96 | 0.26 |
| 30×30×3 | 171 | 0.46 |
| 35×35×3 | 201 | 0.54 |
| 40×40×3 | 231 | 0.62 |
| 50×50×4 | 384 | 1.04 |
| 60×60×5 | 575 | 1.55 |
| 80×80×6 | 924 | 2.49 |
Where the number comes from
The cross-section works out as F = (a + b − t) · t. For 35×35×3 mm that is 201 mm², which at a density of 2.70 g/cm³ gives 0.54 kg/m.
Aluminium is welded with TIG on alternating current or with a wire feeder and aluminium wire; the oxide film melts at around 2050 °C, far above the metal itself, and has to come off with a stainless brush immediately before welding. The detail is in welding aluminium.
How to work out angle mass by hand
An angle is two legs of thickness t that overlap in the corner by a t × t square. Hence the formula F = (a + b − t) · t: the sum of the legs times the thickness, minus the square counted twice. The commonest mistake is to leave out that subtraction — a·t + b·t overstates the area by t / (a + b − t), 3.9 % on a 40×40×3.
Example: 40×40×3 angle, 6 m length.
- Area: (40 + 40 − 3) · 3 = 77 · 3 = 231 mm².
- Mass per metre: 231 × 2.70 / 1000 = 0.624 kg/m.
- A 6 m length: 3.74 kg.
The formula also shows that only the sum of the legs matters for mass, not their ratio: a 50×30×3 unequal angle has exactly the same 231 mm² as a 40×40×3. They behave differently in a structure, but on the scales and in the estimate they are interchangeable.
Example: an angle frame
A 1000×600 mm frame in 30×30×3 angle (from the table above: 171 mm², 0.46 kg/m, exactly 0.462):
- Perimeter: 2 · (1000 + 600) = 3200 mm.
- Mass: 3.2 × 0.462 ≈ 1.48 kg — without welds, bolts or corner gussets.
- One 6 m length makes one such frame with material to spare; ten frames need 32 m, i.e. six lengths — the exact layout with kerfs comes from the bar cutting plan.
A frame in steel angle of the same size would weigh 2.91 times as much, about 4.3 kg. For guard frames, enclosures and racks, that difference is usually what tips the choice to aluminium.
Aluminium versus steel angle
A 40×40×3 angle weighs 1.813 kg/m in steel and 0.624 kg/m in aluminium (0.344 of the mass). But an angle is an open, unsymmetrical section: in bending and compression it twists easily, and aluminium’s modulus of elasticity is a third of steel’s (70 000 against 210 000 MPa). Where an angle carries load, a size-for-size swap from steel to aluminium usually fails — you need a bigger section or a closed profile, which at the same mass is far stiffer in torsion. The mass comparison for tube and box is on the aluminium box section page.
Angle alloys
Aluminium angles are usually extruded in 6xxx alloys; 6060 and 6082 are both 2.70 g/cm³ in the site’s density table, so the masses above apply to them. A 40×40×3 angle in 7075 would weigh 0.649 kg/m (+4.1 %), in 5083 0.614 kg/m. Angles bent from sheet may be 5754 or 1050A (2.67 and 2.70 g/cm³) — within a per cent of the table.
Welding angles
- The leg edge. A fillet laid right at the edge of a thin leg easily melts the edge away — aim the arc more at the thicker member.
- Angle to plate. Thick plate draws heat faster than the angle leg, so the weld tends to lack fusion on the plate side and burn through on the angle side.
- Filler. For 6xxx alloys the site’s filler table names ER 4043 as more resistant to hot cracking and ER 5356 as stronger and colour-stable after anodising (not above 65 °C).
- Distortion. A long weld along a leg bows the angle; weld in short runs, alternating sides.
The full technique is on the welding aluminium page, and the aluminium weight calculator handles every shape. Flat bar — an “unfolded angle” — has its own page: aluminium flat bar.
Common mistakes with angles
- Order of dimensions. 40×40×3 means legs of 40 and 40 and a thickness of 3; entering 3 as a leg gives nonsense.
- Corner not subtracted. a·t + b·t instead of (a + b − t)·t — a few per cent too much on every line.
- Inside leg length. A leg is measured on the outside, from the corner to the toe.
- Steel angle tables as a model. Steel tables include rolling radii in the mass; for aluminium use the formula or the maker’s catalogue.
Frequently asked questions
Does the alloy change the weight?
Barely. The density of aluminium alloys runs between 2.66 and 2.80 g/cm³, and trade calculations use 2.70. Across a whole pallet the difference is smaller than the rolling tolerance, so 2.70 is enough for quoting and haulage.
Why does this differ from the weight at the stockist?
Because the dimensional tolerance works both ways, and sheet and section rarely come out at exactly the nominal thickness. On a thin wall the gap reaches a few per cent — order by the tonne with a margin.
Is a press-braked angle worked out the same way as an extruded one?
Nearly. A bent angle has a radius in the corner instead of a sharp inside corner, so its real area is slightly smaller than (a + b − t) · t. On thin sheet the difference is negligible; the result errs slightly high, which is safe for ordering.
How much does an aluminium angle frame weigh?
The frame perimeter times the mass per metre. A 1000×600 frame in 30×30×3 angle is 3.2 m × 0.462 kg/m ≈ 1.48 kg, without welds or fixings. If the corners are mitred, each side’s cut length equals the frame’s outside dimension.
Updated: