W16×40 vs W18×40
A side-by-side comparison of two AISC wide-flange beams, 16th Edition. Detailing dimensions to the nearest 1/16 in.
W16×40 and W18×40 both weigh 40 lb per foot, so the choice comes down to depth and stiffness rather than weight.
W18×40 is the deeper section at a nominal 18 in., versus 16 in.
W18×40 has the greater bending strength: section modulus Sx of 68.4 in³ versus 64.7, about 6% more.
| Property | W16×40 | W18×40 |
|---|---|---|
| Weight | 40 lb/ft | 40 lb/ft |
| Depth (d) | 16" | 17 7/8" |
| Flange width (bf) | 7" | 6" |
| Web thickness (tw) | 5/16" | 5/16" |
| Flange thickness (tf) | 1/2" | 1/2" |
| Area (A) | 11.8 in² | 11.8 in² |
| Moment of inertia (Ix) | 518 in⁴ | 612 in⁴ |
| Section modulus (Sx) | 64.7 in³ | 68.4 in³ |
| Plastic modulus (Zx) | 73 in³ | 78.4 in³ |
Open W16×40 in the interactive size chart →
Full detail: W16×40 · W18×40. Verify critical dimensions against the current AISC Steel Construction Manual before fabrication.
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