W18x50 — Dimensions, Weight & Section Properties
American wide-flange (W) beam per ASTM A6 / AISC Steel Construction Manual
W18x50 is an American wide-flange beam 18 inches (457.2 mm) deep with a 7.5 in (190.5 mm) flange, weighing 50 pounds per foot (74.4 kg/m) — that is what the "50" 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 | 18 in (457.2 mm) |
| Flange width bf | 7.5 in (190.5 mm) |
| Web thickness tw | 0.355 in (9 mm) |
| Flange thickness tf | 0.57 in (14.5 mm) |
Weight & Cross-Section
| Weight per foot | 50 lb/ft (74.4 kg/m) |
| 20 ft bar | 1,000 lb |
| 40 ft bar | 2,000 lb |
| Area A | 14.7 in² (94.8 cm²) |
Section Properties (strong / weak axis)
| Moment of inertia Ix | 800 in⁴ (33,298 cm⁴) |
| Section modulus Sx | 88.9 in³ (1,457 cm³) |
| Radius of gyration rx | 7.38 in |
| Moment of inertia Iy | 40.1 in⁴ (1,669 cm⁴) |
| Section modulus Sy | 10.7 in³ (175 cm³) |
| Radius of gyration ry | 1.65 in |
Compared with the neighbouring sizes
| Shape | d × bf (in) | lb/ft | Ix (in⁴) | Sx (in³) | Δ weight | Δ Ix |
|---|---|---|---|---|---|---|
| W18x46 | 18.1 × 6.06 | 46 | 712 | 78.8 | −8 % | −11 % |
| W18x50 (this page) | 18 × 7.5 | 50 | 800 | 88.9 | — | — |
| W18x55 | 18.1 × 7.53 | 55 | 890 | 98.3 | +10 % | +11 % |
Deflection example
A simply supported W18x50 spanning 29 ft with a 10 kip point load at midspan deflects 0.38 in (E = 29,000 ksi, Ix = 800 in⁴). The L/360 serviceability limit for this span is 0.97 in — the shape passes this quick check.
Calculate with your own span and load →
Frequently asked questions
How much does a W18x50 beam weigh?
W18x50 weighs 50 pounds per foot (74.4 kg/m). The number after the "x" in the designation is always the weight in lb/ft. A 20 ft bar weighs 1,000 lb and a 40 ft bar 2,000 lb.
What are the dimensions of a W18x50?
W18x50 is 18 in (457.2 mm) deep with a 7.5 in (190.5 mm) wide flange. The web is 0.36 in thick and the flanges are 0.57 in thick. Note the actual depth differs from the nominal W18 label — always design with the actual value.
What are the dimensions of a W18x50 in mm?
W18x50 is 457.2 mm deep with a 190.5 mm wide flange; the web is 9 mm and the flange 14.5 mm thick. In metric section properties: Ix = 33,298 cm⁴, Sx = 1,457 cm³.
How much does a W18x50 weigh in kg?
74.4 kg per meter. A 6 m bar weighs 446 kg and a 12 m bar 893 kg — handy when ordering US shapes from metric suppliers.
What is the moment of inertia of a W18x50?
About the strong axis, Ix = 800 in⁴ (33,298 cm⁴) with section modulus Sx = 88.9 in³. About the weak axis, Iy = 40.1 in⁴ and Sy = 10.7 in³. Use the beam deflection calculator to turn these into deflection and stress for your span and load.
W18x50 or W18x55 — what does one size up change?
W18x55 is about 10% heavier (55 vs 50 lb/ft) but about 11% stiffer (Ix 890 vs 800 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