W8x18 is a wide flange steel beam that is 8.14 in deep with a 5.25 in flange and weighs 18 lb/ft (26.6 kg/m). Its metric designation is W200x26.6. All values below come from the AISC Shapes Database v16.0.
W8x18 Dimensions
| Property | Symbol | Imperial | Metric |
|---|---|---|---|
| Nominal weight | W | 18 lb/ft | 26.6 kg/m |
| Cross-sectional area | A | 5.26 in² | 3,390 mm² |
| Depth | d | 8.14 in | 207 mm |
| Flange width | bf | 5.25 in | 133 mm |
| Web thickness | tw | 0.23 in | 5.84 mm |
| Flange thickness | tf | 0.33 in | 8.38 mm |
| Distance to web toe of fillet (design) | kdes | 0.63 in | 16 mm |
| Distance to web toe of fillet (detailing) | kdet | 0.8125 in | 20.6 mm |
| Web center line to flange toe of fillet | k1 | 0.5625 in | 14.3 mm |
| Distance between web toes of fillets | T | 6.5 in | 165 mm |
| Workable gage (inner holes) | WGi | 2.75 in | 69.9 mm |
W8x18 Section Properties
| Property | Symbol | Imperial | Metric |
|---|---|---|---|
| Moment of inertia, x-axis | Ix | 61.9 in⁴ | 25.8 ×10⁶ mm⁴ |
| Elastic section modulus, x-axis | Sx | 15.2 in³ | 249 ×10³ mm³ |
| Plastic section modulus, x-axis | Zx | 17 in³ | 279 ×10³ mm³ |
| Radius of gyration, x-axis | rx | 3.43 in | 87.1 mm |
| Moment of inertia, y-axis | Iy | 7.97 in⁴ | 3.32 ×10⁶ mm⁴ |
| Elastic section modulus, y-axis | Sy | 3.04 in³ | 49.8 ×10³ mm³ |
| Plastic section modulus, y-axis | Zy | 4.66 in³ | 76.4 ×10³ mm³ |
| Radius of gyration, y-axis | ry | 1.23 in | 31.2 mm |
| Torsional constant | J | 0.172 in⁴ | 71.6 ×10³ mm⁴ |
| Warping constant | Cw | 122 in⁶ | 32.8 ×10⁹ mm⁶ |
| Effective radius of gyration | rts | 1.43 in | 36.3 mm |
| Distance between flange centroids | ho | 7.81 in | 198 mm |
| Flange slenderness | bf/2tf | 7.95 | 7.95 |
| Web slenderness | h/tw | 29.9 | 29.9 |
W8x18 Weight Calculator
Enter a length to get the total weight of a W8x18 beam. A 20 ft length weighs 360 lb.
Uses the AISC nominal weight: 18 lb/ft (26.6 kg/m).
Beams Similar to W8x18
See every W8 size in the W8 beam sizes chart, or compare all shapes in the wide flange beam sizes chart.
W8x18 FAQ
What does W8x18 mean?
W means wide flange. The first number (8) is the nominal depth in inches, and the second number (18) is the weight in pounds per foot. The actual depth of W8x18 is 8.14 in. How to read steel beam sizes.
How much does a W8x18 beam weigh?
W8x18 weighs 18 lb per foot (26.6 kg per meter). A 20 ft beam weighs about 360 lb. Use the calculator above for any length.
What is the metric equivalent of W8x18?
The metric (SI) designation is W200x26.6: 207 mm deep with a 133 mm flange and 26.6 kg/m.
How far can a W8x18 beam span?
Span depends on the load, support conditions, deflection limits and local building code, so it cannot be read from a size table. A licensed structural engineer must size any beam that carries a load.
Source: AISC Shapes Database v16.0, consistent with the AISC Steel Construction Manual, 16th Edition. Last updated: September 2026.
This page is reference information only and is not engineering advice. Do not use it for a specific design without verification by a licensed engineer or architect. Full disclaimer.