W18 Beam Sizes Chart: Weights & Dimensions
There are 23 AISC W18 wide flange sections, running from the W18x35 at 35 lb/ft (17.70 in deep, 6.00 in flange) to the W18x311 at 311 lb/ft (22.32 in deep, 12.005 in flange). The light W18s are everyday floor beams on commercial jobs. The heavy end shows up as transfer girders, heavy industrial framing and the occasional column.
Every size below links to its own page in the steel shapes reference, each with a weight calculator. After the chart: how to read the designation, the three W18 flange groups, where each one turns up on drawings, and how to price them.
W18 Beam Sizes Chart (All 23 AISC Sections)
Weight, depth (d), flange width (bf) and area come from the AISC shapes data behind our shapes pages. Web thickness (tw) and flange thickness (tf) are from the AISC Steel Construction Manual tables. Metric weight is lb/ft × 1.488. For the official numbers, use the AISC Shapes Database v16.0.
| Section | Weight (lb/ft) | Weight (kg/m) | Depth d (in) | Flange width bf (in) | Web tw (in) | Flange tf (in) | Area (in²) |
|---|---|---|---|---|---|---|---|
| W18x35 | 35 | 52.1 | 17.70 | 6.00 | 0.300 | 0.425 | 10.3 |
| W18x40 | 40 | 59.5 | 17.90 | 6.015 | 0.315 | 0.525 | 11.8 |
| W18x46 | 46 | 68.5 | 18.06 | 6.06 | 0.360 | 0.605 | 13.5 |
| W18x50 | 50 | 74.4 | 17.99 | 7.495 | 0.355 | 0.570 | 14.7 |
| W18x55 | 55 | 81.8 | 18.11 | 7.53 | 0.390 | 0.630 | 16.2 |
| W18x60 | 60 | 89.3 | 18.24 | 7.555 | 0.415 | 0.695 | 17.6 |
| W18x65 | 65 | 96.7 | 18.35 | 7.59 | 0.450 | 0.750 | 19.1 |
| W18x71 | 71 | 105.7 | 18.47 | 7.635 | 0.495 | 0.810 | 20.8 |
| W18x76 | 76 | 113.1 | 18.21 | 11.035 | 0.425 | 0.680 | 22.3 |
| W18x86 | 86 | 128.0 | 18.39 | 11.09 | 0.480 | 0.770 | 25.3 |
| W18x97 | 97 | 144.4 | 18.59 | 11.145 | 0.535 | 0.870 | 28.5 |
| W18x106 | 106 | 157.7 | 18.73 | 11.20 | 0.590 | 0.940 | 31.1 |
| W18x119 | 119 | 177.1 | 18.97 | 11.265 | 0.655 | 1.06 | 35.1 |
| W18x130 | 130 | 193.5 | 19.25 | 11.16 | 0.670 | 1.20 | 38.2 |
| W18x143 | 143 | 212.8 | 19.49 | 11.22 | 0.730 | 1.32 | 42.1 |
| W18x158 | 158 | 235.1 | 19.72 | 11.275 | 0.810 | 1.44 | 46.3 |
| W18x175 | 175 | 260.4 | 20.01 | 11.375 | 0.890 | 1.59 | 51.3 |
| W18x192 | 192 | 285.7 | 20.35 | 11.455 | 0.960 | 1.75 | 56.4 |
| W18x211 | 211 | 314.0 | 20.67 | 11.555 | 1.06 | 1.91 | 62.1 |
| W18x234 | 234 | 348.2 | 21.06 | 11.65 | 1.16 | 2.11 | 68.8 |
| W18x258 | 258 | 383.9 | 21.46 | 11.77 | 1.28 | 2.30 | 75.9 |
| W18x283 | 283 | 421.1 | 21.86 | 11.89 | 1.40 | 2.50 | 83.3 |
| W18x311 | 311 | 462.8 | 22.32 | 12.005 | 1.52 | 2.74 | 91.4 |
You can sanity-check any row with one multiplication: steel weighs about 3.4028 lb per foot for every square inch of cross-section. A W18x35 has 10.3 in² of area, and 10.3 × 3.4028 = 35.0 lb/ft. A W18x106 has 31.1 in², and 31.1 × 3.4028 = 105.8 lb/ft, which rounds to the nominal 106. If a number you find somewhere fails this check by more than a pound or so, it's wrong.
What do the numbers in W18x35 mean?
W is the shape type: wide flange, with parallel inner and outer flange faces. 18 is the nominal depth in inches. 35 is the weight in pounds per linear foot.
The weight is the real number. The depth isn't. Across the W18 family, actual depth runs from 17.70 in on the W18x35 to 22.32 in on the W18x311. That happens because mills roll each family with fixed rolls for the inside of the web, then spread the rolls apart to make heavier sections. The flanges get thicker, so the overall depth grows.
That depth growth matters on the drawings. If the architect shows a ceiling plenum built around an 18-inch beam and the engineer bumps a girder to W18x175, it's now 20 inches deep. That's an RFI, not your problem to solve, but it's worth flagging during takeoff.
On metric drawings, a W18x35 is a W460x52, and a W18x50 is a W460x74. The metric number is nominal depth in mm and mass in kg/m.
The shapes and their tolerances are covered by ASTM A6/A6M, the general requirements spec for rolled structural shapes. Most W-shapes in US buildings are specified as ASTM A992, 50 ksi steel.
Light vs heavy W18s: where does each show up?
The W18 family splits cleanly into three flange-width groups. This is the most useful way to think about it for estimating, because flange width tells you the role.
| Group | Sections | Flange width | Typical role on drawings |
|---|---|---|---|
| Light, narrow flange | W18x35, W18x40, W18x46 | about 6 in | Floor beams and infill beams in office, retail, schools |
| Medium | W18x50 to W18x71 | about 7.5 in | Floor beams on longer spans, light girders |
| Heavy, wide flange | W18x76 to W18x311 | about 11 to 12 in | Girders, transfer beams, heavy industrial, some columns |
Light W18s (6-inch flange). The W18x35 is one of the most efficient floor beams in the catalog for its weight, which is why it turns up over and over on composite floor framing. Narrow flanges are fine when the deck and shear studs brace the top flange.
Medium W18s (7.5-inch flange). A W18x50 weighs 43 percent more than a W18x35 and is about the same depth. Engineers go here when the light group runs out of capacity but the depth is fixed by the floor-to-floor height.
Heavy W18s (11-inch flange and up). These look more like columns than beams. You'll see them as girders carrying several beams, transfer girders over openings, and crane or equipment support on industrial jobs. A W18x311 is 311 lb/ft; a 30-foot piece weighs 9,330 lb, which changes your rigging and erection plan.
For structural context, the engineer of record sizes every member. This grouping is a rule of thumb for reading drawings and pricing, not for picking sizes.
Which W18 sizes are most common on commercial drawings?
On typical commercial floor framing, you'll see the light and medium W18s far more than the heavy ones. W18x35, W18x40, W18x46 and W18x50 are everyday beams. The heavy end appears in small quantities on most jobs, if at all.
A practical takeoff note: W18s often appear right next to W16s and W21s on the same plan, and a framing plan with 40 W18x35s spread across 12 sheets is exactly the kind of count where pieces get missed. Group by size, then check each grid bay. If you'd rather not count them by hand, upload a drawing set to SteelFlo and every W18 callout gets boxed and counted, each one tied to a spot on a sheet. The first 3 takeoffs are free.
For the families on either side, see the W12 beam sizes chart and the W14 column sizes chart. The wide flange beam sizes guide covers every depth.
How do you price a W18 by the foot?
Steel is bought by weight, so a W18 prices by its weight per foot:
Material cost per foot = lb/ft × $/lb
Piece weight = lb/ft × length (ft)
Worked example: 24 W18x35 beams at 30 ft each.
- One piece: 35 × 30 = 1,050 lb
- 24 pieces: 1,050 × 24 = 25,200 lb, or 12.6 tons
- At an illustrative $0.70/lb material price: 25,200 × $0.70 = $17,640
Steel prices move month to month, so use a current supplier quote, not the $0.70 above. The full method, including other shape types, is in how to calculate steel beam weight. The free steel weight calculator does the multiplication for any AISC shape and length.
Watch the stock lengths. Service centers commonly carry W-shapes in 20 and 40-foot lengths, and mills roll longer to order. A 30-foot W18x35 from a 40-foot stock length leaves a 10-foot drop. If you can't use that drop elsewhere on the job, it's waste you're paying for. On a list of 24 beams, nesting to stock lengths can change the material number noticeably. The stock lengths and nesting guide walks through the math.
Heavier sections cost more to fabricate in absolute terms (bigger welds, more handling) but often less per pound, because the shop does about the same work on a beam whether it's 35 or 106 lb/ft. Expect your per-pound fabrication rate on a job full of W18x35s to be higher than on one full of W18x106s.
Frequently Asked Questions
What are the dimensions of a W18x35?
A W18x35 is 17.70 inches deep with a 6.00-inch flange, a 0.300-inch web and a 0.425-inch flange thickness. It weighs 35 lb/ft (52.1 kg/m) and has a cross-sectional area of 10.3 in².
How much does a W18x50 weigh?
A W18x50 weighs 50 pounds per linear foot, or 74.4 kg/m. A 20-foot piece weighs 1,000 lb. It's 17.99 inches deep with a 7.495-inch flange.
What is the lightest W18 beam?
The W18x35 is the lightest W18 at 35 lb/ft. The heaviest is the W18x311 at 311 lb/ft, which is over 22 inches deep.
Why is a W18 beam not exactly 18 inches deep?
The 18 is a nominal depth. Mills roll each family from the same inner web dimension and add flange thickness for heavier sections, so actual depth ranges from 17.70 to 22.32 inches across the W18 family.
How much does a W18x40 weigh per foot?
A W18x40 weighs 40 lb/ft, or 59.5 kg/m. It's 17.90 inches deep with a 6.015-inch flange. Multiply 40 by the length in feet to get piece weight.
Bottom line
The W18 chart answers the size question. The slower part of the job is finding how many of each W18 are on the drawings and how long they are. Look up any size on its shapes page, run the weights in the calculator, and when the set has dozens of W18s across many sheets, let SteelFlo's takeoff software count and box them so you can review instead of hunt.