# I-beam sections

Rolled I/H profiles: section families, nominal names versus actual geometry, axes and property units, and the boundary between stock data and structural design.

Reviewed: 2026-11-01

Tags: materials, stock-forms, structural-steel, sections

## Identify the profile family first

British Steel's **203 × 133 × 25 UB** row lists **25.1 kg/m**, so **6.0 m** has an estimated mass of **150.6 kg**, excluding fittings and coatings. The same nominal family contains a different depth and thickness row. Use the exact row and axis sketch for geometry, stiffness and connection checks. [British Steel UB table](https://www.britishsteel.co.uk/wp-content/uploads/2026/02/british-steel-universal-beams-datasheet-190724.pdf)

“I-beam” describes a cross-sectional form, not one interchangeable product. The web connects two flanges, but the flange geometry, dimensions, tolerances and available steel grades depend on the named section family. ArcelorMittal distinguishes **IPE parallel-flange I sections**, **IPN taper-flange I sections**, **HE wide-flange beams**, **UB universal beams**, and American **W wide-flange** and **S standard-beam** products. Keep the family prefix when recording or ordering a section. [ArcelorMittal section families](https://sections.arcelormittal.com/products_and_solutions/EN)

The same producer separates dimensional standards, tolerance standards and steel-grade options. For example, its European IPE/HE/UB entries reference EN 10365 for dimensions and EN 10034 for tolerances, while IPN uses EN 10024 for tolerances. A dimensional family is not a yield-strength grade. [Producer standards and grade matrix](https://sections.arcelormittal.com/products_and_solutions/EN)

This reference concerns stock identification and interpretation. It does not size a member for a building, lifting device or machine frame. See [Stock forms and dimensions](index.md).

## Read nominal names as identifiers

A section designation should lead to an exact table row. It should not be used as a substitute for the row's actual depth, flange width, thicknesses and root geometry. AISC's naming convention represents a US W-shape as nominal depth in inches followed by nominal weight in lb/ft; it separately defines a metric designation using millimeters and kg/m. Unit system and section family must travel with the identifier. [AISC electronic naming convention](https://www.aisc.org/globalassets/aisc/manual/v15.0-shapes-database/naming-convention-for-structural-steel-products-for-use-in-electronic-data-interchange-edi.pdf)

AISC's Shapes Database **v16.0** contains dimensions and properties consistent with its Steel Construction Manual, 16th Edition, in both US customary and metric units. Its historic database is a separate resource for older shapes. A modern catalogue match is therefore not adequate identification of an undocumented existing member. [AISC Shapes Database v16.0](https://www.aisc.org/aisc/publications/steel-construction-manual/aisc-shapes-database-v160/)

When checking an existing section, record measured depth, flange width, web and flange thickness, flange taper and identifying marks. Measurements help narrow the candidate; they do not prove steel grade, toughness or certification. For a new order, retain the full designation, table source/version and material specification, rather than reducing the callout to “200 mm beam.”

## Useful geometry and property fields

Keep the manufacturer's section sketch next to the table. An order or calculation record normally needs:

| Field | What to retain |
| --- | --- |
| Overall depth and flange width | Actual tabulated dimensions, not rounded designation numbers |
| Web and flange thickness | Separate values and any taper convention |
| Root radius / depth between fillets | Connection and fit-up clearance geometry |
| Mass per length / area | Correct units and the exact section row |
| Second moment of area | Axis and fourth-power length unit |
| Elastic / plastic section modulus | Which modulus, axis and cubic length unit |
| Radius of gyration | Axis and length unit |
| Torsional / warping properties | Separate quantities with their own definitions and units |

The Orange Book calculates second moments including tapers, radii and fillets. It defines radius of gyration as `i = sqrt(I/A)` and elastic section modulus as second moment divided by distance to the extreme fiber. It treats the torsional and warping constants separately. A simplified rectangle model can be useful for a check, but should not silently replace published properties for the actual rolled profile. [ArcelorMittal property definitions](https://orangebook.arcelormittal.com/index.php/explanatory-notes/long-products/section-properties)

### Axes and unit traps

Do not map symbols solely by letter. The Orange Book's Eurocode convention uses **x along the member, y as major axis and z as minor axis**, and notes that this differs from earlier UK conventions. Its dimensional values are in mm, while many calculated properties use cm; the warping constant uses dm⁶. The British Steel example below instead labels its cross-section axes x–x and y–y. Compare the sketches and physical bending direction. [Orange Book axes and units](https://orangebook.arcelormittal.com/index.php/explanatory-notes/long-products/general)

A unit conversion raises the conversion factor to the property's power: `1 cm⁴ = 10,000 mm⁴`, whereas `1 cm³ = 1000 mm³`. Confusing the two creates a plausible-looking number with the wrong physical meaning. Preserve units in exported spreadsheets and machine-readable records rather than depending on a heading elsewhere.

## Bounded UB example

British Steel's **203 × 133 × 25 UB** row lists:

| Quantity | Published value |
| --- | --- |
| Mass per length | 25.1 kg/m |
| Overall depth / width | 203.2 / 133.2 mm |
| Web / flange thickness | 5.7 / 7.8 mm |
| Root radius | 7.6 mm |
| Second moments, x–x / y–y | 2340 / 308 cm⁴ |
| Elastic moduli, x–x / y–y | 230 / 46 cm³ |

The table identifies these as dimensions/properties to **BS EN 10365:2017**. The “25” designation is not an exact 25.0 kg/m value, and the same nominal 203×133 family includes another row with different depth and thickness. [British Steel UB data sheet](https://www.britishsteel.co.uk/wp-content/uploads/2026/02/british-steel-universal-beams-datasheet-190724.pdf)

**Original calculations:** a 6.0 m length has nominal mass `25.1 × 6.0 = 150.6 kg`, excluding fittings and coatings. For an illustrative **10 kN·m pure major-axis moment**, the elementary elastic stress estimate is `M/W = 10,000,000 / 230,000 = 43.5 N/mm²`, using the rounded published modulus. About the listed minor axis, the same calculation gives `10,000,000 / 46,000 = 217.4 N/mm²`. This demonstrates axis sensitivity; neither result is a permitted load or complete design check.

## Geometry does not establish member capacity

SteelConstruction.info's member-design guidance separates section classification and cross-section resistance from member buckling, including lateral-torsional buckling under bending, and combined axial/bending checks. Its discussion also distinguishes gross from net sections where holes and openings are present. The cited guidance identifies its basis as first-generation Eurocodes; use the code and National Annex applicable to the project. [Member-design guidance](https://steelconstruction.info/topics/design/member-design/)

Before assigning capacity, resolve grade and thickness-dependent material properties, span, restraints, load position, connections, openings and governing limit states. A catalogue section modulus does not establish lateral restraint or connection adequacy. A mass estimate also cannot serve as a lifting plan: actual length, attached items, lifting points and equipment remain separate requirements.

## Procurement and editions

Specify the complete profile and grade, dimensional/tolerance standards with editions, length and cut tolerances, inspection documents, finish and fabrication requirements. Agree deviations before cutting or drilling; preserve material identification through processing.

British Steel's PDF prints **CUBD:ENG:072024** and **copyright 2024**, although its URL sits in a 2026 upload directory. BSI lists **BS EN 10365:2026**, published July 31, 2026, as current. The cited 2024 producer table's 2017 basis must not be relabeled as independently verified against every 2026 requirement. BSI's scope also excludes stainless-steel hot-rolled sections. [BSI current edition and scope](https://knowledge.bsigroup.com/products/hot-rolled-steel-channels-i-and-h-sections-dimensions-and-masses-1)

The Orange Book's general notes retain a 2017 dimensional-standard basis and cite first-generation design standards. Website copyright years are not technical revisions. Confirm current producer availability and project-specific acceptance requirements rather than treating any historical stock table as a supply guarantee.