W18x158 — Dimensions, Weight & Section Properties
American wide-flange (W) beam per ASTM A6 / AISC Steel Construction Manual
W18x158 is an American wide-flange beam 19.7 inches (500.4 mm) deep with a 11.3 in (287 mm) flange, weighing 158 pounds per foot (235.1 kg/m) — that is what the "158" 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 | 19.7 in (500.4 mm) |
| Flange width bf | 11.3 in (287 mm) |
| Web thickness tw | 0.81 in (20.6 mm) |
| Flange thickness tf | 1.44 in (36.6 mm) |
Weight & Cross-Section
| Weight per foot | 158 lb/ft (235.1 kg/m) |
| 20 ft bar | 3,160 lb |
| 40 ft bar | 6,320 lb |
| Area A | 46.3 in² (298.7 cm²) |
Section Properties (strong / weak axis)
| Moment of inertia Ix | 3,060 in⁴ (127,366 cm⁴) |
| Section modulus Sx | 310 in³ (5,080 cm³) |
| Radius of gyration rx | 8.12 in |
| Moment of inertia Iy | 347 in⁴ (14,443 cm⁴) |
| Section modulus Sy | 61.4 in³ (1,006 cm³) |
| Radius of gyration ry | 2.74 in |
Compared with the neighbouring sizes
| Shape | d × bf (in) | lb/ft | Ix (in⁴) | Sx (in³) | Δ weight | Δ Ix |
|---|---|---|---|---|---|---|
| W18x143 | 19.5 × 11.2 | 143 | 2,750 | 282 | −9 % | −10 % |
| W18x158 (this page) | 19.7 × 11.3 | 158 | 3,060 | 310 | — | — |
| W18x175 | 20 × 11.4 | 175 | 3,450 | 344 | +11 % | +13 % |
Deflection example
A simply supported W18x158 spanning 32 ft with a 10 kip point load at midspan deflects 0.13 in (E = 29,000 ksi, Ix = 3,060 in⁴). The L/360 serviceability limit for this span is 1.07 in — the shape passes this quick check.
Calculate with your own span and load →
Frequently asked questions
How much does a W18x158 beam weigh?
W18x158 weighs 158 pounds per foot (235.1 kg/m). The number after the "x" in the designation is always the weight in lb/ft. A 20 ft bar weighs 3,160 lb and a 40 ft bar 6,320 lb.
What are the dimensions of a W18x158?
W18x158 is 19.7 in (500.4 mm) deep with a 11.3 in (287 mm) wide flange. The web is 0.81 in thick and the flanges are 1.44 in thick. Note the actual depth differs from the nominal W18 label — always design with the actual value.
What are the dimensions of a W18x158 in mm?
W18x158 is 500.4 mm deep with a 287 mm wide flange; the web is 20.6 mm and the flange 36.6 mm thick. In metric section properties: Ix = 127,366 cm⁴, Sx = 5,080 cm³.
How much does a W18x158 weigh in kg?
235.1 kg per meter. A 6 m bar weighs 1,411 kg and a 12 m bar 2,822 kg — handy when ordering US shapes from metric suppliers.
What is the moment of inertia of a W18x158?
About the strong axis, Ix = 3,060 in⁴ (127,366 cm⁴) with section modulus Sx = 310 in³. About the weak axis, Iy = 347 in⁴ and Sy = 61.4 in³. Use the beam deflection calculator to turn these into deflection and stress for your span and load.
W18x158 or W18x175 — what does one size up change?
W18x175 is about 11% heavier (175 vs 158 lb/ft) but about 13% stiffer (Ix 3,450 vs 3,060 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