W 18X60 vs S 18X70
W 18X60 is an W section from the American AISC Shapes Database; S 18X70 is the closest equivalent in the American AISC Shapes Database. They are close to interchangeable in bending: 2015.6 cm³ against 2032 cm³ of plastic modulus, a difference of 0.8%. W 18X60 is the lighter of the two at 89.3 kg/m against 104.2 kg/m, a saving of 14.3% on steel weight. Both are about 460 mm deep, so either fits the same construction zone.
| Property | W 18X60 W | S 18X70 S | Difference |
|---|---|---|---|
| Mass | 89.3 kg/m | 104.2 kg/m | -14.3% |
| Depth | 462.3 mm | 457.2 mm | +1.1% |
| Width | 192 mm | 158.8 mm | +20.9% |
| Web thickness | 10.5 mm | 18.1 mm | -42.0% |
| Flange thickness | 17.7 mm | 17.6 mm | +0.6% |
| Area | 113.5 cm² | 132.3 cm² | -14.2% |
| Second moment, major (Iy) | 40,957 cm⁴ | 38,418 cm⁴ | +6.6% |
| Plastic modulus, major (Wpl,y) | 2,015.6 cm³ | 2,032 cm³ | -0.8% |
| Elastic modulus, major (Wel,y) | 1,769.8 cm³ | 1,687.9 cm³ | +4.9% |
| Second moment, minor (Iz) | 2,085 cm⁴ | 999 cm⁴ | +108.7% |
| Plastic modulus, minor (Wpl,z) | 337.57 cm³ | 234.34 cm³ | +44.1% |
| Radius of gyration, minor (iz) | 4.27 cm | 2.74 cm | +55.8% |
| Torsion constant (It) | 90.32 cm⁴ | 170.7 cm⁴ | -47.1% |
W 18X60 to AISC Shapes Database v16.0; S 18X70 to AISC Shapes Database v16.0. Difference is expressed relative to S 18X70.
How to choose between them
On stiffness, W 18X60 has the larger second moment of area: 40,957 cm⁴ against 38,418 cm⁴, a difference of 6.6%. 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 18X60 is the more efficient section: 22.6 against 19.5 cm³ per kg/m, 15.7% 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 18X60 has 337.57 cm³ of minor-axis plastic modulus against 234.34 cm³, 44.1% 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.
In short, S 18X70 is the stronger section and W 18X60 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.