W8×15 vs W8×18
A side-by-side comparison of two AISC wide-flange beams, 16th Edition. Detailing dimensions to the nearest 1/16 in.
W8×18 is the heavier section at 18 lb per foot, versus 15 for W8×15 (3 lb/ft more).
Both are nominally 8 in. deep.
W8×18 has the greater bending strength: section modulus Sx of 15.2 in³ versus 11.8, about 29% more.
| Property | W8×15 | W8×18 |
|---|---|---|
| Weight | 15 lb/ft | 18 lb/ft |
| Depth (d) | 8 1/8" | 8 1/8" |
| Flange width (bf) | 4" | 5 1/4" |
| Web thickness (tw) | 1/4" | 1/4" |
| Flange thickness (tf) | 5/16" | 5/16" |
| Area (A) | 4.44 in² | 5.26 in² |
| Moment of inertia (Ix) | 48 in⁴ | 61.9 in⁴ |
| Section modulus (Sx) | 11.8 in³ | 15.2 in³ |
| Plastic modulus (Zx) | 13.6 in³ | 17 in³ |
Open W8×15 in the interactive size chart →
Full detail: W8×15 · W8×18. Verify critical dimensions against the current AISC Steel Construction Manual before fabrication.
Browse more: size comparisons · Steel Beam Size Chart