W 12X45 vs H-300x150x11x18
W 12X45 is an W section from the American AISC Shapes Database; H-300x150x11x18 is the closest equivalent in the European (Continental) range. They are close to interchangeable in bending: 1052 cm³ against 1070 cm³ of plastic modulus, a difference of 1.7%. W 12X45 is the lighter of the two at 67 kg/m against 69 kg/m, a saving of 2.9% on steel weight. H-300x150x11x18 is deeper, 318 mm against 307.3 mm, which matters where the floor zone is tight.
| Property | W 12X45 W | H-300x150x11x18 MB & MC | Difference |
|---|---|---|---|
| Mass | 67 kg/m | 69 kg/m | -2.9% |
| Depth | 307.3 mm | 318 mm | -3.4% |
| Width | 204.5 mm | 154 mm | +32.8% |
| Web thickness | 8.5 mm | 11 mm | -22.7% |
| Flange thickness | 14.6 mm | 18 mm | -18.9% |
| Area | 84.5 cm² | 87.9 cm² | -3.9% |
| Second moment, major (Iy) | 14,485 cm⁴ | 14,820 cm⁴ | -2.3% |
| Plastic modulus, major (Wpl,y) | 1,052 cm³ | 1,070 cm³ | -1.7% |
| Elastic modulus, major (Wel,y) | 945.53 cm³ | 932 cm³ | +1.5% |
| Second moment, minor (Iz) | 2,081 cm⁴ | 1,100 cm⁴ | +89.2% |
| Plastic modulus, minor (Wpl,z) | 311.35 cm³ | 223 cm³ | +39.6% |
| Radius of gyration, minor (iz) | 4.95 cm | 3.54 cm | +39.8% |
| Torsion constant (It) | 52.45 cm⁴ | 79 cm⁴ | -33.6% |
W 12X45 to AISC Shapes Database v16.0; H-300x150x11x18 to Continental Steel. Difference is expressed relative to H-300x150x11x18.
How to choose between them
On stiffness, H-300x150x11x18 has the larger second moment of area: 14,820 cm⁴ against 14,485 cm⁴, a difference of 2.3%. 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, the two are equally efficient (15.7 against 15.5 cm³ per kg/m), so on a pure steel-tonnage basis there is nothing to choose between them. The decision comes down to availability, connection detailing and what the rest of the frame uses.
The two diverge much more about the minor axis: W 12X45 has 311.35 cm³ of minor-axis plastic modulus against 223 cm³, 39.6% 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 MB & MC to Continental Steel; 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 2.9% weight.
In short, H-300x150x11x18 is the stronger section and W 12X45 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.