W21x68 — Dimensions, Weight & Section Properties
American wide-flange (W) beam per ASTM A6 / AISC Steel Construction Manual
W21x68 is an American wide-flange beam 21.1 inches (535.9 mm) deep with a 8.27 in (210.1 mm) flange, weighing 68 pounds per foot (101.2 kg/m) — that is what the "68" 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 | 21.1 in (535.9 mm) |
| Flange width bf | 8.27 in (210.1 mm) |
| Web thickness tw | 0.43 in (10.9 mm) |
| Flange thickness tf | 0.685 in (17.4 mm) |
Weight & Cross-Section
| Weight per foot | 68 lb/ft (101.2 kg/m) |
| 20 ft bar | 1,360 lb |
| 40 ft bar | 2,720 lb |
| Area A | 20 in² (129 cm²) |
Section Properties (strong / weak axis)
| Moment of inertia Ix | 1,480 in⁴ (61,602 cm⁴) |
| Section modulus Sx | 140 in³ (2,294 cm³) |
| Radius of gyration rx | 8.6 in |
| Moment of inertia Iy | 64.7 in⁴ (2,693 cm⁴) |
| Section modulus Sy | 15.7 in³ (257 cm³) |
| Radius of gyration ry | 1.8 in |
Compared with the neighbouring sizes
| Shape | d × bf (in) | lb/ft | Ix (in⁴) | Sx (in³) | Δ weight | Δ Ix |
|---|---|---|---|---|---|---|
| W21x62 | 21 × 8.24 | 62 | 1,330 | 127 | −9 % | −10 % |
| W21x68 (this page) | 21.1 × 8.27 | 68 | 1,480 | 140 | — | — |
| W21x73 | 21.2 × 8.3 | 73 | 1,600 | 151 | +7 % | +8 % |
Deflection example
A simply supported W21x68 spanning 34 ft with a 10 kip point load at midspan deflects 0.33 in (E = 29,000 ksi, Ix = 1,480 in⁴). The L/360 serviceability limit for this span is 1.13 in — the shape passes this quick check.
Calculate with your own span and load →
Frequently asked questions
How much does a W21x68 beam weigh?
W21x68 weighs 68 pounds per foot (101.2 kg/m). The number after the "x" in the designation is always the weight in lb/ft. A 20 ft bar weighs 1,360 lb and a 40 ft bar 2,720 lb.
What are the dimensions of a W21x68?
W21x68 is 21.1 in (535.9 mm) deep with a 8.27 in (210.1 mm) wide flange. The web is 0.43 in thick and the flanges are 0.69 in thick. Note the actual depth differs from the nominal W21 label — always design with the actual value.
What are the dimensions of a W21x68 in mm?
W21x68 is 535.9 mm deep with a 210.1 mm wide flange; the web is 10.9 mm and the flange 17.4 mm thick. In metric section properties: Ix = 61,602 cm⁴, Sx = 2,294 cm³.
How much does a W21x68 weigh in kg?
101.2 kg per meter. A 6 m bar weighs 607 kg and a 12 m bar 1,214 kg — handy when ordering US shapes from metric suppliers.
What is the moment of inertia of a W21x68?
About the strong axis, Ix = 1,480 in⁴ (61,602 cm⁴) with section modulus Sx = 140 in³. About the weak axis, Iy = 64.7 in⁴ and Sy = 15.7 in³. Use the beam deflection calculator to turn these into deflection and stress for your span and load.
W21x68 or W21x73 — what does one size up change?
W21x73 is about 7% heavier (73 vs 68 lb/ft) but about 8% stiffer (Ix 1,600 vs 1,480 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