W18x35 — Dimensions, Weight & Section Properties
American wide-flange (W) beam per ASTM A6 / AISC Steel Construction Manual
W18x35 is an American wide-flange beam 17.7 inches (449.6 mm) deep with a 6 in (152.4 mm) flange, weighing 35 pounds per foot (52.1 kg/m) — that is what the "35" 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 | 17.7 in (449.6 mm) |
| Flange width bf | 6 in (152.4 mm) |
| Web thickness tw | 0.3 in (7.6 mm) |
| Flange thickness tf | 0.425 in (10.8 mm) |
Weight & Cross-Section
| Weight per foot | 35 lb/ft (52.1 kg/m) |
| 20 ft bar | 700 lb |
| 40 ft bar | 1,400 lb |
| Area A | 10.3 in² (66.5 cm²) |
Section Properties (strong / weak axis)
| Moment of inertia Ix | 510 in⁴ (21,228 cm⁴) |
| Section modulus Sx | 57.6 in³ (944 cm³) |
| Radius of gyration rx | 7.04 in |
| Moment of inertia Iy | 15.3 in⁴ (637 cm⁴) |
| Section modulus Sy | 5.12 in³ (84 cm³) |
| Radius of gyration ry | 1.22 in |
Compared with the neighbouring sizes
| Shape | d × bf (in) | lb/ft | Ix (in⁴) | Sx (in³) | Δ weight | Δ Ix |
|---|---|---|---|---|---|---|
| W18x35 (this page) | 17.7 × 6 | 35 | 510 | 57.6 | — | — |
| W18x40 | 17.9 × 6.02 | 40 | 612 | 68.4 | +14 % | +20 % |
Deflection example
A simply supported W18x35 spanning 28 ft with a 10 kip point load at midspan deflects 0.53 in (E = 29,000 ksi, Ix = 510 in⁴). The L/360 serviceability limit for this span is 0.93 in — the shape passes this quick check.
Calculate with your own span and load →
Frequently asked questions
How much does a W18x35 beam weigh?
W18x35 weighs 35 pounds per foot (52.1 kg/m). The number after the "x" in the designation is always the weight in lb/ft. A 20 ft bar weighs 700 lb and a 40 ft bar 1,400 lb.
What are the dimensions of a W18x35?
W18x35 is 17.7 in (449.6 mm) deep with a 6 in (152.4 mm) wide flange. The web is 0.3 in thick and the flanges are 0.43 in thick. Note the actual depth differs from the nominal W18 label — always design with the actual value.
What are the dimensions of a W18x35 in mm?
W18x35 is 449.6 mm deep with a 152.4 mm wide flange; the web is 7.6 mm and the flange 10.8 mm thick. In metric section properties: Ix = 21,228 cm⁴, Sx = 944 cm³.
How much does a W18x35 weigh in kg?
52.1 kg per meter. A 6 m bar weighs 313 kg and a 12 m bar 625 kg — handy when ordering US shapes from metric suppliers.
What is the moment of inertia of a W18x35?
About the strong axis, Ix = 510 in⁴ (21,228 cm⁴) with section modulus Sx = 57.6 in³. About the weak axis, Iy = 15.3 in⁴ and Sy = 5.12 in³. Use the beam deflection calculator to turn these into deflection and stress for your span and load.
W18x35 or W18x40 — what does one size up change?
W18x40 is about 14% heavier (40 vs 35 lb/ft) but about 20% stiffer (Ix 612 vs 510 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