W8×21 vs W8×24
A side-by-side comparison of two AISC wide-flange beams, 16th Edition. Detailing dimensions to the nearest 1/16 in.
W8×24 is the heavier section at 24 lb per foot, versus 21 for W8×21 (3 lb/ft more).
Both are nominally 8 in. deep.
W8×24 has the greater bending strength: section modulus Sx of 20.9 in³ versus 18.2, about 15% more.
| Property | W8×21 | W8×24 |
|---|---|---|
| Weight | 21 lb/ft | 24 lb/ft |
| Depth (d) | 8 1/4" | 7 7/8" |
| Flange width (bf) | 5 1/4" | 6 1/2" |
| Web thickness (tw) | 1/4" | 1/4" |
| Flange thickness (tf) | 3/8" | 3/8" |
| Area (A) | 6.16 in² | 7.08 in² |
| Moment of inertia (Ix) | 75.3 in⁴ | 82.7 in⁴ |
| Section modulus (Sx) | 18.2 in³ | 20.9 in³ |
| Plastic modulus (Zx) | 20.4 in³ | 23.1 in³ |
Open W8×21 in the interactive size chart →
Full detail: W8×21 · W8×24. Verify critical dimensions against the current AISC Steel Construction Manual before fabrication.
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