W21×55 vs W21×57
A side-by-side comparison of two AISC wide-flange beams, 16th Edition. Detailing dimensions to the nearest 1/16 in.
W21×57 is the heavier section at 57 lb per foot, versus 55 for W21×55 (2 lb/ft more).
Both are nominally 21 in. deep.
W21×57 has the greater bending strength: section modulus Sx of 111 in³ versus 110, about 1% more.
| Property | W21×55 | W21×57 |
|---|---|---|
| Weight | 55 lb/ft | 57 lb/ft |
| Depth (d) | 20 3/4" | 21" |
| Flange width (bf) | 8 1/4" | 6 1/2" |
| Web thickness (tw) | 3/8" | 3/8" |
| Flange thickness (tf) | 1/2" | 5/8" |
| Area (A) | 16.2 in² | 16.7 in² |
| Moment of inertia (Ix) | 1140 in⁴ | 1170 in⁴ |
| Section modulus (Sx) | 110 in³ | 111 in³ |
| Plastic modulus (Zx) | 126 in³ | 129 in³ |
Open W21×55 in the interactive size chart →
Full detail: W21×55 · W21×57. Verify critical dimensions against the current AISC Steel Construction Manual before fabrication.
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