W18x311 — Dimensions, Weight & Section Properties
American wide-flange (W) beam per ASTM A6 / AISC Steel Construction Manual
W18x311 is an American wide-flange beam 22.3 inches (566.4 mm) deep with a 12 in (304.8 mm) flange, weighing 311 pounds per foot (462.8 kg/m) — that is what the "311" 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 | 22.3 in (566.4 mm) |
| Flange width bf | 12 in (304.8 mm) |
| Web thickness tw | 1.52 in (38.6 mm) |
| Flange thickness tf | 2.74 in (69.6 mm) |
Weight & Cross-Section
| Weight per foot | 311 lb/ft (462.8 kg/m) |
| 20 ft bar | 6,220 lb |
| 40 ft bar | 12,440 lb |
| Area A | 91.6 in² (591 cm²) |
Section Properties (strong / weak axis)
| Moment of inertia Ix | 6,970 in⁴ (290,112 cm⁴) |
| Section modulus Sx | 624 in³ (10,225 cm³) |
| Radius of gyration rx | 8.72 in |
| Moment of inertia Iy | 795 in⁴ (33,090 cm⁴) |
| Section modulus Sy | 132 in³ (2,163 cm³) |
| Radius of gyration ry | 2.95 in |
Compared with the neighbouring sizes
| Shape | d × bf (in) | lb/ft | Ix (in⁴) | Sx (in³) | Δ weight | Δ Ix |
|---|---|---|---|---|---|---|
| W18x283 | 21.9 × 11.9 | 283 | 6,170 | 565 | −9 % | −11 % |
| W18x311 (this page) | 22.3 × 12 | 311 | 6,970 | 624 | — | — |
Deflection example
A simply supported W18x311 spanning 36 ft with a 10 kip point load at midspan deflects 0.08 in (E = 29,000 ksi, Ix = 6,970 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 W18x311 beam weigh?
W18x311 weighs 311 pounds per foot (462.8 kg/m). The number after the "x" in the designation is always the weight in lb/ft. A 20 ft bar weighs 6,220 lb and a 40 ft bar 12,440 lb.
What are the dimensions of a W18x311?
W18x311 is 22.3 in (566.4 mm) deep with a 12 in (304.8 mm) wide flange. The web is 1.52 in thick and the flanges are 2.74 in thick. Note the actual depth differs from the nominal W18 label — always design with the actual value.
What are the dimensions of a W18x311 in mm?
W18x311 is 566.4 mm deep with a 304.8 mm wide flange; the web is 38.6 mm and the flange 69.6 mm thick. In metric section properties: Ix = 290,112 cm⁴, Sx = 10,225 cm³.
How much does a W18x311 weigh in kg?
462.8 kg per meter. A 6 m bar weighs 2,777 kg and a 12 m bar 5,554 kg — handy when ordering US shapes from metric suppliers.
What is the moment of inertia of a W18x311?
About the strong axis, Ix = 6,970 in⁴ (290,112 cm⁴) with section modulus Sx = 624 in³. About the weak axis, Iy = 795 in⁴ and Sy = 132 in³. Use the beam deflection calculator to turn these into deflection and stress for your span and load.
W18x311 or W18x283 — what does one size down change?
W18x283 is about 9% lighter (283 vs 311 lb/ft) but about 11% less stiff (Ix 6,170 vs 6,970 in⁴). Check deflection before downsizing — stiffness falls much faster than weight.
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