W12x87 — Dimensions, Weight & Section Properties
American wide-flange (W) beam per ASTM A6 / AISC Steel Construction Manual
W12x87 is an American wide-flange beam 12.5 inches (317.5 mm) deep with a 12.1 in (307.3 mm) flange, weighing 87 pounds per foot (129.5 kg/m) — that is what the "87" 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 | 12.5 in (317.5 mm) |
| Flange width bf | 12.1 in (307.3 mm) |
| Web thickness tw | 0.515 in (13.1 mm) |
| Flange thickness tf | 0.81 in (20.6 mm) |
Weight & Cross-Section
| Weight per foot | 87 lb/ft (129.5 kg/m) |
| 20 ft bar | 1,740 lb |
| 40 ft bar | 3,480 lb |
| Area A | 25.6 in² (165.2 cm²) |
Section Properties (strong / weak axis)
| Moment of inertia Ix | 740 in⁴ (30,801 cm⁴) |
| Section modulus Sx | 118 in³ (1,934 cm³) |
| Radius of gyration rx | 5.38 in |
| Moment of inertia Iy | 241 in⁴ (10,031 cm⁴) |
| Section modulus Sy | 39.7 in³ (651 cm³) |
| Radius of gyration ry | 3.07 in |
Compared with the neighbouring sizes
| Shape | d × bf (in) | lb/ft | Ix (in⁴) | Sx (in³) | Δ weight | Δ Ix |
|---|---|---|---|---|---|---|
| W12x79 | 12.4 × 12.1 | 79 | 662 | 107 | −9 % | −11 % |
| W12x87 (this page) | 12.5 × 12.1 | 87 | 740 | 118 | — | — |
| W12x96 | 12.7 × 12.2 | 96 | 833 | 131 | +10 % | +13 % |
Deflection example
A simply supported W12x87 spanning 20 ft with a 10 kip point load at midspan deflects 0.13 in (E = 29,000 ksi, Ix = 740 in⁴). The L/360 serviceability limit for this span is 0.67 in — the shape passes this quick check.
Calculate with your own span and load →
Frequently asked questions
How much does a W12x87 beam weigh?
W12x87 weighs 87 pounds per foot (129.5 kg/m). The number after the "x" in the designation is always the weight in lb/ft. A 20 ft bar weighs 1,740 lb and a 40 ft bar 3,480 lb.
What are the dimensions of a W12x87?
W12x87 is 12.5 in (317.5 mm) deep with a 12.1 in (307.3 mm) wide flange. The web is 0.52 in thick and the flanges are 0.81 in thick. Note the actual depth differs from the nominal W12 label — always design with the actual value.
What are the dimensions of a W12x87 in mm?
W12x87 is 317.5 mm deep with a 307.3 mm wide flange; the web is 13.1 mm and the flange 20.6 mm thick. In metric section properties: Ix = 30,801 cm⁴, Sx = 1,934 cm³.
How much does a W12x87 weigh in kg?
129.5 kg per meter. A 6 m bar weighs 777 kg and a 12 m bar 1,554 kg — handy when ordering US shapes from metric suppliers.
What is the moment of inertia of a W12x87?
About the strong axis, Ix = 740 in⁴ (30,801 cm⁴) with section modulus Sx = 118 in³. About the weak axis, Iy = 241 in⁴ and Sy = 39.7 in³. Use the beam deflection calculator to turn these into deflection and stress for your span and load.
W12x87 or W12x96 — what does one size up change?
W12x96 is about 10% heavier (96 vs 87 lb/ft) but about 13% stiffer (Ix 833 vs 740 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