W21x166 — Dimensions, Weight & Section Properties
American wide-flange (W) beam per ASTM A6 / AISC Steel Construction Manual
W21x166 is an American wide-flange beam 22.5 inches (571.5 mm) deep with a 12.4 in (315 mm) flange, weighing 166 pounds per foot (247 kg/m) — that is what the "166" 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 | 22.5 in (571.5 mm) |
| Flange width bf | 12.4 in (315 mm) |
| Web thickness tw | 0.75 in (19 mm) |
| Flange thickness tf | 1.36 in (34.5 mm) |
Weight & Cross-Section
| Weight per foot | 166 lb/ft (247 kg/m) |
| 20 ft bar | 3,320 lb |
| 40 ft bar | 6,640 lb |
| Area A | 48.8 in² (314.8 cm²) |
Section Properties (strong / weak axis)
| Moment of inertia Ix | 4,280 in⁴ (178,146 cm⁴) |
| Section modulus Sx | 380 in³ (6,227 cm³) |
| Radius of gyration rx | 9.36 in |
| Moment of inertia Iy | 435 in⁴ (18,106 cm⁴) |
| Section modulus Sy | 70 in³ (1,147 cm³) |
| Radius of gyration ry | 2.99 in |
Compared with the neighbouring sizes
| Shape | d × bf (in) | lb/ft | Ix (in⁴) | Sx (in³) | Δ weight | Δ Ix |
|---|---|---|---|---|---|---|
| W21x147 | 22.1 × 12.5 | 147 | 3,630 | 329 | −11 % | −15 % |
| W21x166 (this page) | 22.5 × 12.4 | 166 | 4,280 | 380 | — | — |
| W21x182 | 22.7 × 12.5 | 182 | 4,730 | 417 | +10 % | +11 % |
Deflection example
A simply supported W21x166 spanning 36 ft with a 10 kip point load at midspan deflects 0.14 in (E = 29,000 ksi, Ix = 4,280 in⁴). The L/360 serviceability limit for this span is 1.2 in — the shape passes this quick check.
Calculate with your own span and load →
Frequently asked questions
How much does a W21x166 beam weigh?
W21x166 weighs 166 pounds per foot (247 kg/m). The number after the "x" in the designation is always the weight in lb/ft. A 20 ft bar weighs 3,320 lb and a 40 ft bar 6,640 lb.
What are the dimensions of a W21x166?
W21x166 is 22.5 in (571.5 mm) deep with a 12.4 in (315 mm) wide flange. The web is 0.75 in thick and the flanges are 1.36 in thick. Note the actual depth differs from the nominal W21 label — always design with the actual value.
What are the dimensions of a W21x166 in mm?
W21x166 is 571.5 mm deep with a 315 mm wide flange; the web is 19 mm and the flange 34.5 mm thick. In metric section properties: Ix = 178,146 cm⁴, Sx = 6,227 cm³.
How much does a W21x166 weigh in kg?
247 kg per meter. A 6 m bar weighs 1,482 kg and a 12 m bar 2,964 kg — handy when ordering US shapes from metric suppliers.
What is the moment of inertia of a W21x166?
About the strong axis, Ix = 4,280 in⁴ (178,146 cm⁴) with section modulus Sx = 380 in³. About the weak axis, Iy = 435 in⁴ and Sy = 70 in³. Use the beam deflection calculator to turn these into deflection and stress for your span and load.
W21x166 or W21x182 — what does one size up change?
W21x182 is about 10% heavier (182 vs 166 lb/ft) but about 11% stiffer (Ix 4,730 vs 4,280 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