W21x83 — Dimensions, Weight & Section Properties
American wide-flange (W) beam per ASTM A6 / AISC Steel Construction Manual
W21x83 is an American wide-flange beam 21.4 inches (543.6 mm) deep with a 8.36 in (212.3 mm) flange, weighing 83 pounds per foot (123.5 kg/m) — that is what the "83" in the designation means. All values below are the standard AISC published section properties used in US structural design, with metric equivalents alongside.
Typical uses: floor and roof framing, columns, headers, and general steel construction. For a quick stiffness check, see the deflection example below or open the beam calculator with your own span and load.
Dimensions
| Depth d | 21.4 in (543.6 mm) |
| Flange width bf | 8.36 in (212.3 mm) |
| Web thickness tw | 0.515 in (13.1 mm) |
| Flange thickness tf | 0.835 in (21.2 mm) |
Weight & Cross-Section
| Weight per foot | 83 lb/ft (123.5 kg/m) |
| 20 ft bar | 1,660 lb |
| 40 ft bar | 3,320 lb |
| Area A | 24.4 in² (157.4 cm²) |
Section Properties (strong / weak axis)
| Moment of inertia Ix | 1,830 in⁴ (76,170 cm⁴) |
| Section modulus Sx | 171 in³ (2,802 cm³) |
| Radius of gyration rx | 8.67 in |
| Moment of inertia Iy | 81.4 in⁴ (3,388 cm⁴) |
| Section modulus Sy | 19.5 in³ (320 cm³) |
| Radius of gyration ry | 1.83 in |
Compared with the neighbouring sizes
| Shape | d × bf (in) | lb/ft | Ix (in⁴) | Sx (in³) | Δ weight | Δ Ix |
|---|---|---|---|---|---|---|
| W21x73 | 21.2 × 8.3 | 73 | 1,600 | 151 | −12 % | −13 % |
| W21x83 (this page) | 21.4 × 8.36 | 83 | 1,830 | 171 | — | — |
| W21x93 | 21.6 × 8.42 | 93 | 2,070 | 192 | +12 % | +13 % |
Deflection example
A simply supported W21x83 spanning 34 ft with a 10 kip point load at midspan deflects 0.27 in (E = 29,000 ksi, Ix = 1,830 in⁴). The L/360 serviceability limit for this span is 1.13 in — the shape passes this quick check.
Calculate with your own span and load →
Frequently asked questions
How much does a W21x83 beam weigh?
W21x83 weighs 83 pounds per foot (123.5 kg/m). The number after the "x" in the designation is always the weight in lb/ft. A 20 ft bar weighs 1,660 lb and a 40 ft bar 3,320 lb.
What are the dimensions of a W21x83?
W21x83 is 21.4 in (543.6 mm) deep with a 8.36 in (212.3 mm) wide flange. The web is 0.52 in thick and the flanges are 0.84 in thick. Note the actual depth differs from the nominal W21 label — always design with the actual value.
What are the dimensions of a W21x83 in mm?
W21x83 is 543.6 mm deep with a 212.3 mm wide flange; the web is 13.1 mm and the flange 21.2 mm thick. In metric section properties: Ix = 76,170 cm⁴, Sx = 2,802 cm³.
How much does a W21x83 weigh in kg?
123.5 kg per meter. A 6 m bar weighs 741 kg and a 12 m bar 1,482 kg — handy when ordering US shapes from metric suppliers.
What is the moment of inertia of a W21x83?
About the strong axis, Ix = 1,830 in⁴ (76,170 cm⁴) with section modulus Sx = 171 in³. About the weak axis, Iy = 81.4 in⁴ and Sy = 19.5 in³. Use the beam deflection calculator to turn these into deflection and stress for your span and load.
W21x83 or W21x93 — what does one size up change?
W21x93 is about 12% heavier (93 vs 83 lb/ft) but about 13% stiffer (Ix 2,070 vs 1,830 in⁴). Going one step up within the same depth group is usually the cheapest way to cut deflection.
Values are entered from the governing standard’s published tables and cross-checked programmatically against its mass and section formulas before publication. Spotted an error? Write to advertising@metalabout.net — verified corrections ship within days. About