W18x71 — Dimensions, Weight & Section Properties
American wide-flange (W) beam per ASTM A6 / AISC Steel Construction Manual
W18x71 is an American wide-flange beam 18.5 inches (469.9 mm) deep with a 7.64 in (194.1 mm) flange, weighing 71 pounds per foot (105.7 kg/m) — that is what the "71" 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 | 18.5 in (469.9 mm) |
| Flange width bf | 7.64 in (194.1 mm) |
| Web thickness tw | 0.495 in (12.6 mm) |
| Flange thickness tf | 0.81 in (20.6 mm) |
Weight & Cross-Section
| Weight per foot | 71 lb/ft (105.7 kg/m) |
| 20 ft bar | 1,420 lb |
| 40 ft bar | 2,840 lb |
| Area A | 20.9 in² (134.8 cm²) |
Section Properties (strong / weak axis)
| Moment of inertia Ix | 1,170 in⁴ (48,699 cm⁴) |
| Section modulus Sx | 127 in³ (2,081 cm³) |
| Radius of gyration rx | 7.5 in |
| Moment of inertia Iy | 60.3 in⁴ (2,510 cm⁴) |
| Section modulus Sy | 15.8 in³ (259 cm³) |
| Radius of gyration ry | 1.7 in |
Compared with the neighbouring sizes
| Shape | d × bf (in) | lb/ft | Ix (in⁴) | Sx (in³) | Δ weight | Δ Ix |
|---|---|---|---|---|---|---|
| W18x65 | 18.4 × 7.59 | 65 | 1,070 | 117 | −8 % | −9 % |
| W18x71 (this page) | 18.5 × 7.64 | 71 | 1,170 | 127 | — | — |
| W18x76 | 18.2 × 11 | 76 | 1,330 | 146 | +7 % | +14 % |
Deflection example
A simply supported W18x71 spanning 30 ft with a 10 kip point load at midspan deflects 0.29 in (E = 29,000 ksi, Ix = 1,170 in⁴). The L/360 serviceability limit for this span is 1 in — the shape passes this quick check.
Calculate with your own span and load →
Frequently asked questions
How much does a W18x71 beam weigh?
W18x71 weighs 71 pounds per foot (105.7 kg/m). The number after the "x" in the designation is always the weight in lb/ft. A 20 ft bar weighs 1,420 lb and a 40 ft bar 2,840 lb.
What are the dimensions of a W18x71?
W18x71 is 18.5 in (469.9 mm) deep with a 7.64 in (194.1 mm) wide flange. The web is 0.5 in thick and the flanges are 0.81 in thick. Note the actual depth differs from the nominal W18 label — always design with the actual value.
What are the dimensions of a W18x71 in mm?
W18x71 is 469.9 mm deep with a 194.1 mm wide flange; the web is 12.6 mm and the flange 20.6 mm thick. In metric section properties: Ix = 48,699 cm⁴, Sx = 2,081 cm³.
How much does a W18x71 weigh in kg?
105.7 kg per meter. A 6 m bar weighs 634 kg and a 12 m bar 1,268 kg — handy when ordering US shapes from metric suppliers.
What is the moment of inertia of a W18x71?
About the strong axis, Ix = 1,170 in⁴ (48,699 cm⁴) with section modulus Sx = 127 in³. About the weak axis, Iy = 60.3 in⁴ and Sy = 15.8 in³. Use the beam deflection calculator to turn these into deflection and stress for your span and load.
W18x71 or W18x76 — what does one size up change?
W18x76 is about 7% heavier (76 vs 71 lb/ft) but about 14% stiffer (Ix 1,330 vs 1,170 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