W 6X20 vs H-150x150x7x10-31.1
W 6X20 is an W section from the American AISC Shapes Database; H-150x150x7x10-31.1 is the closest equivalent in the European (Continental) range. They are close to interchangeable in bending: 244.17 cm³ against 243 cm³ of plastic modulus, a difference of 0.5%. W 6X20 is the lighter of the two at 29.8 kg/m against 31.1 kg/m, a saving of 4.2% on steel weight. W 6X20 is deeper, 157.5 mm against 150 mm, which matters where the floor zone is tight.
| Property | W 6X20 W | H-150x150x7x10-31.1 MB & MC | Difference |
|---|---|---|---|
| Mass | 29.8 kg/m | 31.1 kg/m | -4.2% |
| Depth | 157.5 mm | 150 mm | +5.0% |
| Width | 152.9 mm | 150 mm | +1.9% |
| Web thickness | 6.6 mm | 7 mm | -5.7% |
| Flange thickness | 9.3 mm | 10 mm | -7.0% |
| Area | 37.9 cm² | 39.6 cm² | -4.3% |
| Second moment, major (Iy) | 1,723 cm⁴ | 1,623 cm⁴ | +6.2% |
| Plastic modulus, major (Wpl,y) | 244.17 cm³ | 243 cm³ | +0.5% |
| Elastic modulus, major (Wel,y) | 219.59 cm³ | 216 cm³ | +1.7% |
| Second moment, minor (Iz) | 553.6 cm⁴ | 563 cm⁴ | -1.7% |
| Plastic modulus, minor (Wpl,z) | 110.12 cm³ | 114 cm³ | -3.4% |
| Radius of gyration, minor (iz) | 3.81 cm | 3.77 cm | +1.1% |
| Torsion constant (It) | 9.99 cm⁴ | 12.5 cm⁴ | -20.1% |
W 6X20 to AISC Shapes Database v16.0; H-150x150x7x10-31.1 to Continental Steel. Difference is expressed relative to H-150x150x7x10-31.1.
How to choose between them
On stiffness, W 6X20 has the larger second moment of area: 1,723 cm⁴ against 1,623 cm⁴, a difference of 6.2%. 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, W 6X20 is the more efficient section: 8.2 against 7.8 cm³ per kg/m, 4.9% 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.
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 4.2% weight.
In short, W 6X20 is the stronger section and W 6X20 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.