W 12X79 vs HP 12X84
W 12X79 is an W section from the American AISC Shapes Database; HP 12X84 is the closest equivalent in the American AISC Shapes Database. They are close to interchangeable in bending: 1950.1 cm³ against 1966.4 cm³ of plastic modulus, a difference of 0.8%. W 12X79 is the lighter of the two at 117.6 kg/m against 125 kg/m, a saving of 5.9% on steel weight. Both are about 314 mm deep, so either fits the same construction zone.
| Property | W 12X79 W | HP 12X84 HP | Difference |
|---|---|---|---|
| Mass | 117.6 kg/m | 125 kg/m | -5.9% |
| Depth | 315 mm | 312.4 mm | +0.8% |
| Width | 307.3 mm | 312.4 mm | -1.6% |
| Web thickness | 11.9 mm | 17.4 mm | -31.6% |
| Flange thickness | 18.7 mm | 17.4 mm | +7.5% |
| Area | 149.7 cm² | 158.7 cm² | -5.7% |
| Second moment, major (Iy) | 27,555 cm⁴ | 27,055 cm⁴ | +1.8% |
| Plastic modulus, major (Wpl,y) | 1,950.1 cm³ | 1,966.4 cm³ | -0.8% |
| Elastic modulus, major (Wel,y) | 1,753.4 cm³ | 1,737 cm³ | +0.9% |
| Second moment, minor (Iz) | 8,991 cm⁴ | 8,866 cm⁴ | +1.4% |
| Plastic modulus, minor (Wpl,z) | 889.82 cm³ | 871.79 cm³ | +2.1% |
| Radius of gyration, minor (iz) | 7.75 cm | 7.47 cm | +3.7% |
| Torsion constant (It) | 159.8 cm⁴ | 176.5 cm⁴ | -9.5% |
W 12X79 to AISC Shapes Database v16.0; HP 12X84 to AISC Shapes Database v16.0. Difference is expressed relative to HP 12X84.
How to choose between them
On stiffness, W 12X79 has the larger second moment of area: 27,555 cm⁴ against 27,055 cm⁴, a difference of 1.8%. 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 12X79 is the more efficient section: 16.6 against 15.7 cm³ per kg/m, 5.4% 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.
In short, HP 12X84 is the stronger section and W 12X79 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.