W21x101 — Dimensions, Weight & Section Properties
American wide-flange (W) beam per ASTM A6 / AISC Steel Construction Manual
W21x101 is an American wide-flange beam 21.4 inches (543.6 mm) deep with a 12.3 in (312.4 mm) flange, weighing 101 pounds per foot (150.3 kg/m) — that is what the "101" 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 | 21.4 in (543.6 mm) |
| Flange width bf | 12.3 in (312.4 mm) |
| Web thickness tw | 0.5 in (12.7 mm) |
| Flange thickness tf | 0.8 in (20.3 mm) |
Weight & Cross-Section
| Weight per foot | 101 lb/ft (150.3 kg/m) |
| 20 ft bar | 2,020 lb |
| 40 ft bar | 4,040 lb |
| Area A | 29.8 in² (192.3 cm²) |
Section Properties (strong / weak axis)
| Moment of inertia Ix | 2,420 in⁴ (100,728 cm⁴) |
| Section modulus Sx | 227 in³ (3,720 cm³) |
| Radius of gyration rx | 9.02 in |
| Moment of inertia Iy | 248 in⁴ (10,323 cm⁴) |
| Section modulus Sy | 40.3 in³ (660 cm³) |
| Radius of gyration ry | 2.89 in |
Compared with the neighbouring sizes
| Shape | d × bf (in) | lb/ft | Ix (in⁴) | Sx (in³) | Δ weight | Δ Ix |
|---|---|---|---|---|---|---|
| W21x93 | 21.6 × 8.42 | 93 | 2,070 | 192 | −8 % | −14 % |
| W21x101 (this page) | 21.4 × 12.3 | 101 | 2,420 | 227 | — | — |
| W21x111 | 21.5 × 12.3 | 111 | 2,670 | 249 | +10 % | +10 % |
Deflection example
A simply supported W21x101 spanning 34 ft with a 10 kip point load at midspan deflects 0.2 in (E = 29,000 ksi, Ix = 2,420 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 W21x101 beam weigh?
W21x101 weighs 101 pounds per foot (150.3 kg/m). The number after the "x" in the designation is always the weight in lb/ft. A 20 ft bar weighs 2,020 lb and a 40 ft bar 4,040 lb.
What are the dimensions of a W21x101?
W21x101 is 21.4 in (543.6 mm) deep with a 12.3 in (312.4 mm) wide flange. The web is 0.5 in thick and the flanges are 0.8 in thick. Note the actual depth differs from the nominal W21 label — always design with the actual value.
What are the dimensions of a W21x101 in mm?
W21x101 is 543.6 mm deep with a 312.4 mm wide flange; the web is 12.7 mm and the flange 20.3 mm thick. In metric section properties: Ix = 100,728 cm⁴, Sx = 3,720 cm³.
How much does a W21x101 weigh in kg?
150.3 kg per meter. A 6 m bar weighs 902 kg and a 12 m bar 1,804 kg — handy when ordering US shapes from metric suppliers.
What is the moment of inertia of a W21x101?
About the strong axis, Ix = 2,420 in⁴ (100,728 cm⁴) with section modulus Sx = 227 in³. About the weak axis, Iy = 248 in⁴ and Sy = 40.3 in³. Use the beam deflection calculator to turn these into deflection and stress for your span and load.
W21x101 or W21x111 — what does one size up change?
W21x111 is about 10% heavier (111 vs 101 lb/ft) but about 10% stiffer (Ix 2,670 vs 2,420 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