A36 steel is the standard carbon structural steel in the US, covered by ASTM A36, with a specified minimum yield strength of 36 ksi and a tensile strength of 58 to 80 ksi. It is the everyday grade for plate, angles, channels, bars and many small shapes because it is cheap, widely stocked and easy to weld, cut and drill.
If you are buying plate for a base plate, angle for a ledger or flat bar for brackets, A36 is probably what the supplier will hand you unless you ask for something else. Wide flange beams are a different story, and that is covered below.
What the A36 Specification Covers
The ASTM A36/A36M scope (checked October 2026) describes it as carbon steel shapes, plates and bars of structural quality for riveted, bolted or welded construction of bridges and buildings, and for general structural purposes. The standard sets the chemistry limits (carbon, manganese, phosphorus, sulfur, silicon and copper) and the tensile properties each heat has to meet, which is why it can be ordered by name with no further description.
Two details in the scope are worth knowing:
- It is hot rolled product. A36 covers plate, bar and rolled shapes. It does not cover sheet, tube or cold-formed studs, which have their own specs. The difference is explained in our hot rolled vs cold rolled steel guide.
- Welding still needs a procedure. The standard itself says a welding procedure suited to the grade and the intended service has to be used. A36 is forgiving, but it is not exempt from proper welding practice.
A36 Steel Properties
The numbers that matter for design and ordering are the specified minimums. The figures below are the specified values for A36 plate as listed in an AISC survey of mill test reports, Brockenbrough’s MTR Survey of Plate Material Used in Structural Fabrication (AISC Engineering Journal, first quarter 2003, read October 2026).
| Property | A36 (specified) |
|---|---|
| Minimum yield strength | 36 ksi |
| Tensile strength | 58 ksi min, 80 ksi max |
| Product forms | Plate, bar, rolled shapes |
| Type | Carbon steel, hot rolled |
Steel density does not change with grade, so A36 weighs the same as any other carbon steel. Using the usual 490 lb per cubic foot, one square foot of plate weighs about 40.8 lb for every inch of thickness, so 1/2 inch plate is about 20.4 lb per square foot and 1/4 inch plate about 10.2 lb.
Actual strength is usually higher than 36 ksi
Mill test reports almost always show a yield point above the minimum. In the same AISC survey, A36 plate from 0.188 to 0.75 inch thick (14,900 test results) averaged a yield point of 46.9 ksi, and plate over 0.75 to 4.00 inch averaged 43.1 ksi. Thicker plate tends to come in lower, which is normal for rolled steel.
That extra strength is not something you can design with. Calculations use the specified 36 ksi, because any given piece only has to meet the minimum. The survey matters for a different reason: in seismic design and in capacity checks, a member that is stronger than expected can push more force into its connections, so engineers sometimes have to account for the expected strength as well as the minimum.
A36 vs A992 vs A572 Grade 50
These three grades cover most of the structural steel bought in the US. The short version: A36 for plate and small shapes, A992 for wide flange beams and columns, A572 Grade 50 when you need 50 ksi in plate or other shapes.
| A36 | A572 Grade 50 | A992 | |
|---|---|---|---|
| Minimum yield | 36 ksi | 50 ksi | 50 ksi |
| Minimum tensile | 58 ksi (80 max) | 65 ksi | 65 ksi |
| Steel type | Carbon | High-strength low-alloy | Shapes grade with tighter chemistry and a capped yield-to-tensile ratio |
| Typical use | Plate, bar, angles, channels, base plates, gussets | Plate and shapes where 50 ksi is needed | Wide flange (W) beams and columns |
A36 and A572 Grade 50 values are from the AISC mill test survey cited above. A992 limits and the reasons it replaced A36 for W shapes are explained on our ASTM A992 steel page. In short, wide flange beams used to be ordered as A36, but mills were routinely producing steel well above 36 ksi, and A992 brought the minimum up to 50 ksi with limits on the upper end.
Can you swap A36 for a 50 ksi grade?
Going up in grade is usually harmless for strength, but it is not automatic. A 50 ksi plate can change the weld procedure, and in seismic frames a stronger-than-specified part can overload the connection next to it. Going down, from a specified 50 ksi grade to A36, is never a field decision. Any substitution on a structural part should go through the engineer of record.
What A36 Is Used For
- Plate: column base plates, gusset plates, stiffeners, shear tabs and embed plates. Base plate sizing is covered in our base plate guide.
- Angles: lintels, ledgers, bracing and clip angles. Sizes and weights are in the angle iron sizes chart.
- Channels: stair stringers, light framing, trailer and equipment frames. See the C channel sizes chart.
- Flat and round bar: brackets, hangers, handrail parts and general fabrication.
For a feel of the weights involved, here are three common A36 shapes from the AISC Shapes Database v16.0:
| Shape | Weight (lb/ft) | Area (in²) |
|---|---|---|
| L3x3x1/4 angle | 4.9 | 1.44 |
| L4x4x1/4 angle | 6.6 | 1.93 |
| C6x8.2 channel | 8.2 | 2.39 |
The shape dimensions are the same whatever the grade. Grade changes the strength, not the size or weight.
Working With A36: Welding, Cutting and Finishing
Welding
A36 is one of the easiest structural steels to weld. The AISC survey’s chemistry analysis found it generally showed good weldability. Common stick, MIG and flux-core filler metals rated at 70 ksi tensile are routinely used with it, but the specific electrode, any preheat for thick plate and the joint details belong in a written procedure. If the part is galvanized, the coating changes the job, as covered in our guide to welding galvanized steel.
Cutting and drilling
A36 cuts cleanly with a torch, plasma or band saw and drills with standard high-speed steel bits. Because it is relatively soft, it is a good choice for parts that need lots of holes, such as connection plates.
Corrosion
A36 is plain carbon steel and rusts if left bare outdoors. It arrives with mill scale that has to be removed before painting, or it can be hot-dip galvanized. It is not a weathering steel, so it will not form a protective patina the way A588 does.
Ordering A36: What to Ask For
- Name the spec and grade: “ASTM A36” on the order, not just “mild steel” or “hot rolled”.
- Ask for the mill test report if the part is structural. It shows the heat number, chemistry and actual tensile results.
- Check dual certification. Plate is often certified to more than one spec, such as A36 and A572 Grade 50, which is fine as long as it meets what your drawing calls for.
- Give sizes the supplier can stock: standard plate thicknesses and standard angle and channel sizes are faster and cheaper than odd ones.
Whatever the grade, a part that carries load, from a beam seat to a base plate, has to be sized and checked by a licensed structural engineer. Knowing the grade is only one input to that calculation.
A36 Steel FAQ
Is A36 steel the same as mild steel?
Close, but not exactly. “Mild steel” is a loose term for low-carbon steel. A36 is a specific ASTM standard with guaranteed minimum strength and chemistry limits. Most A36 would be called mild steel, but not all mild steel meets A36.
Are steel I-beams made from A36?
Wide flange beams in US buildings are normally A992 today. A36 was the usual grade for W shapes in the past, so older buildings often have A36 beams. S-shapes, channels and angles are still commonly supplied in A36.
What does the 36 in A36 mean?
It matches the specified minimum yield strength, 36 ksi (about 250 MPa). The “A” is the ASTM prefix for ferrous materials.
Is A36 steel stainless or rust resistant?
No. It is plain carbon steel and needs paint, galvanizing or another coating for outdoor or wet service.
Can A36 be heat treated to make it harder?
Not usefully. Its low carbon content means quenching does little, so it is not chosen where hardness or wear resistance matters. Abrasion-resistant plate grades are made for that job.
The Short Version
A36 is the default US carbon structural steel: 36 ksi minimum yield, 58 to 80 ksi tensile, cheap, stocked everywhere and easy to fabricate. Use it for plate, angles, channels and bar. Expect wide flange beams to be A992 instead, and let the engineer of record approve any change of grade on a structural part.
Reference information only, not engineering advice. Disclaimer.