The Question Buyers Get Wrong: H-Beam and I-Beam Are Not the Same Profile
The confusion is understandable, because both profiles look like the letter they are named after and both are sold as structural steel. But in a design office they are different sections with different rules, and using one where the other is specified can fail a load check or waste steel. This is not a language problem; it is real. An H-beam with a nominal 200 mm depth and an I-beam with a nominal 200 mm depth carry very different bending moments.
The clean way to separate them is to look at the flanges. An I-beam has tapered inner flange faces and flanges that are roughly half the depth of the section. An H-beam (also called a wide-flange beam) has parallel flanges with constant thickness, and the flange width is often close to or greater than the section depth. That geometry is the whole story, because it controls the section modulus and the bending capacity.
Where the Difference Actually Shows Up
The flange shape drives three things that matter to a buyer.
- Bending capacity. Parallel wide flanges put more material far from the neutral axis, which raises the section modulus and the moment of inertia for the same weight.
- Connection design. Parallel flanges are easy to bolt and weld; tapered flanges need tapered washers or special detailing.
- Availability. H-beams are produced in a wide matrix of sizes under EN 10025 and ASTM; I-beams follow a smaller, older size table under JIS G3101 and GB/T 706.
Compare the Numbers
Nothing settles the argument like a side-by-side table. All three sections below are nominally 200 mm deep, but they are not interchangeable.
| Section | Depth h (mm) | Flange width b (mm) | Web t (mm) | Flange t (mm) | Weight (kg/m) | Ix (cm4) | Wx (cm3) |
|---|---|---|---|---|---|---|---|
| IPE 200 (H, parallel) | 200 | 100 | 5.6 | 8.5 | 22.4 | 1943 | 194 |
| HEA 200 (H, wide) | 190 | 200 | 6.5 | 10.0 | 42.3 | 3692 | 389 |
| I-beam 200 (tapered) | 200 | 100 | 7.0 | 11.4 | 27.9 | 2140 | 214 |
Read the table again. HEA 200 is almost twice the weight of IPE 200 but carries roughly double the moment, so it is efficient when the load is heavy and the depth is capped. The tapered I-beam 200 sits between them in weight but is weaker than HEA 200 for the same depth because its narrower flange puts less material at the extreme fibres.
When to Choose an H-Beam
- Columns. Wide parallel flanges give a stable, compact column with good buckling resistance in both axes.
- Moment frames and portal frames. Welded or bolted moment connections are far easier on a parallel flange.
- Long spans and heavy loads. The higher section modulus per kilogram usually wins the steel quantity comparison.
- Multi-storey and pre-engineered buildings. Standard H sizes are stocked and easily spliced.
If a structural drawing shows a full building frame, the answer is almost always an H-beam, most commonly S235JR, S355JR or ASTM A992.
When to Choose an I-Beam
- Light floor beams, purlins and girts. The tapered profile is adequate at short spans and small loads.
- Monorails and crane rails (light duty). The tapered flange suits a specific range of standard trolley wheels.
- Cost-sensitive simple frames where a local fabricator already owns I-beam stock and tooling.
- Legacy drawings. Where a design was written to an older national standard, matching the original section avoids rechecking the frame.
A tapered I-beam is not a weaker H-beam; it is a different, older section family, and it is entirely correct where the design says so.
Standards You Need on the Purchase Order
The named size is not enough. Fix the standard, the grade and the dimensional tolerance.
| Requirement | Typical options | Notes |
|---|---|---|
| Standard | EN 10025, ASTM A6/A992, JIS G3101, GB/T 11263 | Match the design code |
| Grade | S235JR, S355JR, S355J2, SS400, A36, A992 | Grade drives yield strength |
| Dimensional tolerance | EN 10034, ASTM A6 | Flange and depth tolerances differ |
| Length | Fixed or random 6-12 m | Cut lengths add cost |
| Test certificate | EN 10204 3.1 | Request heat and mechanicals |
S235JR and SS400 are commonly treated as equivalent in casual buying, but their chemical and mechanical specs are not identical. If the design code is European, buy EN 10025 with a 3.1 certificate rather than substituting.
Send us the section schedule, the standard and grade, the total tonnage and your discharge port, and we will quote H-beams and I-beams side by side so you can compare on the section that actually carries the load.
Need a Quotation for Your Project?
Send us the grade or standard, size, quantity and destination port. Our export team replies with a full quotation, usually within 12 hours.