W8x15 — Dimensions, Weight & Section Properties
American wide-flange (W) beam per ASTM A6 / AISC Steel Construction Manual
W8x15 is an American wide-flange beam 8.11 inches (206 mm) deep with a 4.02 in (102.1 mm) flange, weighing 15 pounds per foot (22.3 kg/m) — that is what the "15" 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 | 8.11 in (206 mm) |
| Flange width bf | 4.02 in (102.1 mm) |
| Web thickness tw | 0.245 in (6.2 mm) |
| Flange thickness tf | 0.315 in (8 mm) |
Weight & Cross-Section
| Weight per foot | 15 lb/ft (22.3 kg/m) |
| 20 ft bar | 300 lb |
| 40 ft bar | 600 lb |
| Area A | 4.44 in² (28.6 cm²) |
Section Properties (strong / weak axis)
| Moment of inertia Ix | 48 in⁴ (1,998 cm⁴) |
| Section modulus Sx | 11.8 in³ (193 cm³) |
| Radius of gyration rx | 3.29 in |
| Moment of inertia Iy | 3.41 in⁴ (142 cm⁴) |
| Section modulus Sy | 1.7 in³ (28 cm³) |
| Radius of gyration ry | 0.88 in |
Compared with the neighbouring sizes
| Shape | d × bf (in) | lb/ft | Ix (in⁴) | Sx (in³) | Δ weight | Δ Ix |
|---|---|---|---|---|---|---|
| W8x13 | 7.99 × 4 | 13 | 39.6 | 9.91 | −13 % | −17 % |
| W8x15 (this page) | 8.11 × 4.02 | 15 | 48 | 11.8 | — | — |
| W8x18 | 8.14 × 5.25 | 18 | 61.9 | 15.2 | +20 % | +29 % |
Deflection example
A simply supported W8x15 spanning 13 ft with a 10 kip point load at midspan deflects 0.57 in (E = 29,000 ksi, Ix = 48 in⁴). The L/360 serviceability limit for this span is 0.43 in — the shape does NOT pass this quick check.
Calculate with your own span and load →
Frequently asked questions
How much does a W8x15 beam weigh?
W8x15 weighs 15 pounds per foot (22.3 kg/m). The number after the "x" in the designation is always the weight in lb/ft. A 20 ft bar weighs 300 lb and a 40 ft bar 600 lb.
What are the dimensions of a W8x15?
W8x15 is 8.11 in (206 mm) deep with a 4.02 in (102.1 mm) wide flange. The web is 0.25 in thick and the flanges are 0.32 in thick. Note the actual depth differs from the nominal W8 label — always design with the actual value.
What are the dimensions of a W8x15 in mm?
W8x15 is 206 mm deep with a 102.1 mm wide flange; the web is 6.2 mm and the flange 8 mm thick. In metric section properties: Ix = 1,998 cm⁴, Sx = 193 cm³.
How much does a W8x15 weigh in kg?
22.3 kg per meter. A 6 m bar weighs 134 kg and a 12 m bar 268 kg — handy when ordering US shapes from metric suppliers.
What is the moment of inertia of a W8x15?
About the strong axis, Ix = 48 in⁴ (1,998 cm⁴) with section modulus Sx = 11.8 in³. About the weak axis, Iy = 3.41 in⁴ and Sy = 1.7 in³. Use the beam deflection calculator to turn these into deflection and stress for your span and load.
W8x15 or W8x18 — what does one size up change?
W8x18 is about 20% heavier (18 vs 15 lb/ft) but about 29% stiffer (Ix 61.9 vs 48 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