How much weight a steel angle can support depends on how it's loaded: as a beam (lintel, ledger, shelf), in tension (hanger, brace) or in compression (strut, leg). Angle is efficient in tension. A small L51x51x6.4 (2x2x1/4) in 300W steel has a gross yielding resistance of about 164 kN before bolt holes and connection effects are checked. As a beam or a strut it's much weaker, because an angle bends about tilted principal axes, twists easily and buckles at modest lengths. That's also why angle iron flexes. Here's what controls angle capacity, with real section values.
Treat the numbers here as explanations, not designs. A loaded angle in a building needs a designer or engineer, and structural work usually needs a permit.
Four ways an angle carries load
The question "how much can angle iron hold?" has a different answer for each job:
- Bending (lintels, ledgers, shelf angles, frames). The angle spans between supports. Capacity falls with the square of the span; stiffness falls with the cube. Deflection usually governs.
- Tension (hangers, X-bracing, ties). The whole cross-section works evenly, so angle is efficient. Connections and bolt holes usually decide the capacity.
- Compression (struts, legs, posts, bracing). Angles buckle at loads well below yield because their weakest radius of gyration is small. Length matters enormously.
- Cantilevers and brackets. A short angle bolted to a wall carrying a load on its outstanding leg. The leg bends like a little cantilever plate, and the bolts and the wall take the pull.
Does angle iron flex or bend?
Yes, and for three reasons that don't apply as much to beams and tubes:
- Its weakest axis is diagonal. An angle's principal axes are tilted. For an equal-leg L102x102x6.4, the stiffness about its weakest axis is only about 40% of its stiffness about the horizontal axis. Load it vertically without restraint and it deflects downward and sideways at the same time.
- It twists easily. Thin, open shapes have very little torsional stiffness, and an angle's shear centre sits at the corner where the legs meet. Loads on the outstanding leg are offset from that point and twist the angle.
- It's light for its size. Angle is often chosen for its low weight, so it's naturally flexible compared with the members around it.
Flexing within the elastic range is normal and recovers when the load comes off. If the angle is loaded past its yield strength, it bends permanently. A noticeably sagging or twisted angle lintel or ledger is a warning sign that needs a designer to look at it.
Steel angle stiffness chart: size and orientation
Since deflection usually governs angles in bending, stiffness (the moment of inertia, I) is the number to compare. Values are from the AISC Shapes Database metric columns for the equivalent imperial angles, about the horizontal axis with the angle restrained from rolling.
| Angle | Mass (kg/m) | I (10⁶ mm⁴) | Stiffness relative to L76x76x6.4 |
|---|---|---|---|
| L76x76x6.4 | 7.3 | 0.51 | 1.0 |
| L76x76x9.5 | 10.7 | 0.73 | 1.4 |
| L102x102x6.4 | 9.8 | 1.25 | 2.4 |
| L102x102x12.7 | 19.0 | 2.30 | 4.5 |
| L127x89x7.9, long leg vertical | 12.9 | 2.74 | 5.4 |
| L152x102x7.9, long leg vertical | 15.3 | 4.75 | 9.3 |
| L152x102x7.9, long leg horizontal | 15.3 | 1.72 | 3.4 |
Three takeaways:
- Leg length beats thickness. Doubling the L102x102's thickness doubles its weight but adds only about 84% stiffness. The L152x102x7.9 is lighter than the L102x102x12.7 yet about twice as stiff with its long leg vertical.
- Orientation matters. The same L152x102x7.9 loses almost two thirds of its stiffness when the long leg is laid flat. Long leg vertical is the rule for lintels and ledgers.
- Restraint matters. These values assume the angle can't roll. Unrestrained angles bend about their tilted principal axes and deflect more.
For a full worked bending and deflection check, see our steel angle lintel design example. In that example, a 3.0 m brick veneer opening needs an L127x89x7.9, strength uses under 40% of capacity, and deflection (span/700, the basis of the Ontario lintel tables) governs.
Angle in tension and compression
Tension. Under CSA S16, a tension member is checked for yielding of the gross section and for fracture of the net section at the connection. Gross yielding is simple: Tr = φ x A x Fy. For an L51x51x6.4 (area 609 mm²) in 300W steel:
Tr = 0.90 x 609 x 300 = 164 kN, roughly the weight of 16.7 tonnes.
That's an upper bound. Bolt holes remove area, and when only one leg is connected, the stress doesn't spread evenly across the other leg (called shear lag). The net-section check uses the steel's ultimate strength, a lower resistance factor and a reduced effective area, and it often governs. The bolts and welds then have to carry the load too.
Compression. Here the length controls everything. The L51x51x6.4's smallest radius of gyration is only about 9.8 mm, so a strut just 1.5 m long already has a slenderness ratio over 150. CSA S16 limits how slender a compression member may be, and single angles connected by one leg also carry bending from the eccentric connection. Compression capacity of angle struts comes from the S16 column formulas, worked by a designer for the actual length and end connections. Don't expect an angle "leg" or post to carry anything close to its tension capacity.
Steel angle design: what an engineer checks
A steel angle design, for a lintel, ledger or brace, typically covers:
- Loads, factored by the building code. In the 2024 Ontario Building Code the usual floor combination is 1.25 x dead + 1.5 x live (Table 4.1.3.2.-A).
- Bending resistance, including how a single angle behaves about its principal axes and whether it's restrained.
- Deflection, using unfactored loads and a limit suited to what the angle supports.
- Tension or compression resistance, with the effective length and connection eccentricity.
- Connections: bolts, welds, bearing and the material the angle attaches to.
- Rotation and twist, especially when the load sits on the outstanding leg.
For lintels in Part 9 houses, the Ontario Building Code's lintel tables set minimum angles, so many openings never need a calculation. See can you use angle iron as a lintel.
When angle isn't the answer
Angle is cheap, easy to connect and good at many jobs, but if your angle is flexing or twisting, the fix is usually a different shape rather than a thicker angle:
- Longer spans or real loads: a C-channel braced along its length, or a W-shape. See C-channel load capacity.
- Posts and struts: HSS tube, which has no weak diagonal axis.
- Custom leg sizes or a sharp corner: bent plate. Our steel angle vs bent plate comparison covers the trade-offs.
- Heavy masonry or floor loads over openings: a beam with a welded plate instead of a loose angle.
Getting angles cut, punched and fabricated
We supply steel angle cut to length, with holes, slots and welded clips as detailed, including angle lintels for masonry openings. Send the drawings or an engineer's schedule, and tell us the finish you need.
Request a quote with your drawings, or see our steel products for lintels, plates, channels and beams.
Frequently asked questions
How much weight can angle iron hold?
It depends on how the angle is used. In tension, a small L51x51x6.4 in 300W steel has a gross yielding resistance of about 164 kN before hole and connection checks. As a beam or a strut it carries far less, and the amount drops quickly as the span or length grows.
Does angle iron flex?
Yes. Angle is light and open, so it is flexible for its weight, especially about its weakest (diagonal) axis and in twisting. Within its elastic range it springs back when the load comes off; loaded past yield, it bends permanently.
Which way should angle iron face for the most strength?
For bending, put the longer leg vertical. An L152x102x7.9 is about 2.8 times stiffer with the 152 mm leg vertical than with it horizontal. The horizontal leg should also be restrained, by masonry, a deck or fasteners, so the angle can't roll.
Is thicker angle much stronger?
Less than people expect. Doubling the thickness of an L102x102 from 6.4 mm to 12.7 mm roughly doubles the weight but raises bending stiffness only about 1.8 times. A longer leg usually adds stiffness more efficiently than a thicker one.
