W 33X201 vs UB 914×305×289
W 33X201 is an W section from the American AISC Shapes Database; UB 914×305×289 is the closest equivalent in the UK Blue Book (SCI P363). They are close to interchangeable in bending: 12667.2 cm³ against 12600 cm³ of plastic modulus, a difference of 0.5%. UB 914×305×289 is the lighter of the two at 289.1 kg/m against 299.1 kg/m, a saving of 3.5% on steel weight. UB 914×305×289 is deeper, 926.6 mm against 856 mm, which matters where the floor zone is tight.
| Property | W 33X201 W | UB 914×305×289 UB | Difference |
|---|---|---|---|
| Mass | 299.1 kg/m | 289.1 kg/m | +3.5% |
| Depth | 856 mm | 926.6 mm | -7.6% |
| Width | 398.8 mm | 307.7 mm | +29.6% |
| Web thickness | 18.2 mm | 19.5 mm | -6.7% |
| Flange thickness | 29.2 mm | 32 mm | -8.8% |
| Area | 381.3 cm² | 368 cm² | +3.6% |
| Second moment, major (Iy) | 482,828 cm⁴ | 504,000 cm⁴ | -4.2% |
| Plastic modulus, major (Wpl,y) | 12,667.2 cm³ | 12,600 cm³ | +0.5% |
| Elastic modulus, major (Wel,y) | 11,241.5 cm³ | 10,900 cm³ | +3.1% |
| Second moment, minor (Iz) | 31,176 cm⁴ | 15,600 cm⁴ | +99.8% |
| Plastic modulus, minor (Wpl,z) | 2,408.9 cm³ | 1,600 cm³ | +50.6% |
| Radius of gyration, minor (iz) | 9.04 cm | 6.51 cm | +38.9% |
| Torsion constant (It) | 865.8 cm⁴ | 926 cm⁴ | -6.5% |
W 33X201 to AISC Shapes Database v16.0; UB 914×305×289 to BS EN 10365:2017. Difference is expressed relative to UB 914×305×289.
How to choose between them
On stiffness, UB 914×305×289 has the larger second moment of area: 504,000 cm⁴ against 482,828 cm⁴, a difference of 4.2%. This matters more often than the strength comparison, because on normal floor spans deflection rather than bending capacity sets the beam size - so if the two are close on modulus but apart on inertia, the stiffer one is usually the better answer even when it is not the stronger one.
Measured as bending capacity per kilogram of steel, UB 914×305×289 is the more efficient section: 43.6 against 42.4 cm³ per kg/m, 2.8% better. Over a floor of repeated beams that difference is real tonnage, though it is often outweighed by whichever section the fabricator can actually source.
The two diverge much more about the minor axis: W 33X201 has 2408.9 cm³ of minor-axis plastic modulus against 1600 cm³, 50.6% more. If the member sees any minor-axis bending, or if it is unrestrained over a long length and lateral-torsional buckling governs, that gap decides the comparison even though the major-axis numbers looked equivalent.
These come from different catalogues, so treat the swap as a design change rather than a like-for-like substitution. W sections are specified to AISC Shapes Database v16.0 and UB to BS EN 10365:2017; the steel grades, tolerances and available lengths differ, connection details and bolt gauges are set out differently, and the two are rarely both stocked in the same market. Check availability before changing a section on a drawing to save 3.5% weight.
In short, W 33X201 is the stronger section and UB 914×305×289 is the lighter one; where those are the same section, it is the clear choice, and where they are not, decide on whether your design is governed by capacity or by tonnage.