The AISC catalog lists 13 W8 wide flange shapes, running from the W8x10 at 10 lb/ft (14.9 kg/m) up to the W8x67 at 67 lb/ft (99.7 kg/m). All of them are nominally 8 inches deep, but actual depth ranges from 7.89" to 9.00", and flange width ranges from about 4" to about 8.3". That flange spread is the thing to understand about W8s: the light end is a narrow beam, and the heavy end is a nearly square column section.
The full chart is below, followed by where W8s land on real drawings and how to handle them in a takeoff. Every size links to its own page in the steel shapes reference with a weight calculator and example cost.
W8 Beam Sizes Chart (All 13 AISC Sections)
Weights are from the AISC shape database. Metric weight is lb/ft × 1.488. Depth (d) and flange width (bf) are actual dimensions, not nominal.
| Section | Weight (lb/ft) | Weight (kg/m) | Depth d (in) | Flange width bf (in) | Area (in²) |
|---|---|---|---|---|---|
| W8x10 | 10 | 14.9 | 7.89 | 3.94 | 2.96 |
| W8x13 | 13 | 19.3 | 7.99 | 4 | 3.84 |
| W8x15 | 15 | 22.3 | 8.11 | 4.015 | 4.44 |
| W8x18 | 18 | 26.8 | 8.14 | 5.25 | 5.26 |
| W8x21 | 21 | 31.3 | 8.28 | 5.27 | 6.16 |
| W8x24 | 24 | 35.7 | 7.93 | 6.495 | 7.08 |
| W8x28 | 28 | 41.7 | 8.06 | 6.535 | 8.25 |
| W8x31 | 31 | 46.1 | 8.00 | 7.995 | 9.13 |
| W8x35 | 35 | 52.1 | 8.12 | 8.02 | 10.3 |
| W8x40 | 40 | 59.5 | 8.25 | 8.07 | 11.7 |
| W8x48 | 48 | 71.4 | 8.50 | 8.11 | 14.1 |
| W8x58 | 58 | 86.3 | 8.75 | 8.22 | 17.1 |
| W8x67 | 67 | 99.7 | 9.00 | 8.28 | 19.7 |
A quick way to sanity-check any row: for a steel W shape, area (in²) × 3.40 is very close to weight (lb/ft). A W8x31 has 9.13 in² of steel, and 9.13 × 3.4028 = 31.07 lb/ft. If a number from some other source fails that check, it's probably a typo.
How to Read a W8 Designation
W8x31 means a wide flange shape, nominal depth 8 inches, weighing 31 pounds per linear foot. The weight is exact and is the only number you need for tonnage. The depth is nominal: a W8x10 is actually 7.89" deep and a W8x67 is 9.00" deep. The heavier shapes get deeper because the mill keeps the inside dimension between flanges roughly fixed and adds material to the outside, so thicker flanges push the overall depth up.
Metric drawings (Canada, some US federal work) call the same shapes by millimetre depth and kg/m. The W8x18, for example, is a W200x26.6. The W-shape metric equivalents guide has the full crosswalk if you're converting a metric BOM.
The Four W8 Flange Families
The 13 W8s are really four groups that share a flange width. This matters on takeoff because two sections with nearby weights can look nothing alike on a detail.
| Family | Sections | Flange width | What it behaves like |
|---|---|---|---|
| Narrow | W8x10, W8x13, W8x15 | about 4" | Light beam, infill, bracing strut |
| Medium-narrow | W8x18, W8x21 | about 5.25" | Short-span beam, lintel |
| Medium | W8x24, W8x28 | about 6.5" | Beam or light post |
| Column (near-square) | W8x31 through W8x67 | about 8" to 8.3" | Posts and columns |
Notice that the W8x24 is actually shallower (7.93") than the W8x21 (8.28"). When the flange family changes, depth resets. If you're checking a detail dimension against a callout, use the actual depth from the chart rather than assuming heavier means deeper.
Where W8s Show Up on Drawings
W8s are a small-building and secondary-framing shape. On the drawing sets we see most often, they appear in a handful of predictable places:
- Posts and light columns. The W8x31 is probably the most common W8 on any drawing. It's the go-to post for canopies, one-story additions, mezzanine columns, and pipe-rack legs. W8x24, W8x35, and W8x40 show up in the same role when loads are lighter or heavier.
- Mezzanine and platform framing. Short beams and joists-in-steel on equipment platforms and storage mezzanines. The mezzanine takeoff guide walks through a full example.
- Lintels and openings. W8x18 and W8x21 appear over wider openings in masonry and at overhead doors where a loose angle won't carry the wall. Check whether a bearing plate is welded on; see the lintel takeoff guide.
- Roof screens, dunnage, and equipment support. RTU frames and screen posts on the roof sheets, often buried in the mechanical coordination details.
- Bracing struts and infill. W8x10 through W8x15 as struts, header beams at roof openings, and edge framing.
Sizes and spans in this post are for estimating and budgeting. The structural engineer of record selects members; nothing here is a design recommendation.
How Estimators Price W8s
W8s are light, so the material dollars per piece are small. The cost is in handling. A shop spends about the same time cutting, drilling, and fitting a clip on a W8x10 as it does on a W8x31, and the fabrication hours per ton on light shapes run much higher than on heavy framing. If you price W8 miscellaneous framing at the same dollars per ton as your W24 floor beams, you'll lose money on it. The fabrication man-hours per ton guide covers why piece count drives labor more than tonnage.
A worked example. Say a canopy has 12 posts, each a W8x31 at 14'-0", plus 16 W8x18 beams at 18'-0".
- Posts: 12 × 14 ft × 31 lb/ft = 5,208 lb
- Beams: 16 × 18 ft × 18 lb/ft = 5,184 lb
- Total: 10,392 lb, or about 5.2 tons before connections and waste
Now price it. As an assumption for illustration only, use $0.60/lb for delivered material. That's about $6,235 in steel. Then add base plates (every post gets one, plus anchor rods; the base plate and anchor bolt guide has the checklist), cap plates, beam connections, and shop labor per piece. On a small canopy like this, the fittings and labor usually cost more than the W8s themselves.
Nesting. Plenty of service centers stock light beams only in 40-foot lengths, so 14-foot posts nest only two to a stick with a 12-foot drop. A 60-foot stick takes four with a 4-foot drop, which is a real saving if your supplier carries them. Run the numbers before you assume 60s are available; the stock lengths and nesting guide explains how to pick mults.
Takeoff Mistakes With W8s
Missing them entirely. W8s live on the architectural, mechanical, and detail sheets as often as on the framing plans. Roof dunnage and screen posts are the classic miss: the structural plans say "see mechanical," and the steel ends up in nobody's bid.
Mixing up W8x28 and W8x18. On a low-resolution scan, a stray mark turns 18 into 28. The weight difference is 56%, and the flange width jumps from 5.25" to 6.5". If a lintel callout reads W8x28 on a 6-foot opening while the one next to it reads W8x18, check it.
Reading W8 as W6 or W10. The same scan problem at the depth digit. A W6x15 and a W8x15 have the same weight but different depths, which matters for fit-up even if it doesn't change tonnage.
Pricing posts as beams. A W8x31 post carries a base plate, cap plate, and maybe anchor rods and a leveling nut setup. A W8x31 beam carries two clips. Keep them as separate line items even when the section is the same.
SteelFlo reads W8 callouts off every sheet of a PDF, including the detail and mechanical sheets where they tend to hide, and builds the takeoff with weights filled in from the catalog. Try it on a drawing set.
For the rest of the wide flange family, the full W-shape size chart covers every depth from W4 to W44 on one page, and the free steel weight calculator handles any W8 at any length.
Frequently Asked Questions
How much does a W8x31 weigh?
A W8x31 weighs 31 pounds per linear foot, or 46.1 kg/m. A 20-foot W8x31 weighs 620 lb. Its actual depth is 8.00" and its flange is 7.995" wide, which makes it close to square and a common choice for posts and light columns.
What is the lightest W8 beam?
The W8x10 is the lightest W8 in the AISC catalog at 10 lb/ft (14.9 kg/m). It is 7.89" deep with a 3.94" flange. It usually appears as infill framing, a strut, or a header at a roof opening.
What is the heaviest W8?
The W8x67 is the heaviest W8 at 67 lb/ft (99.7 kg/m). It is 9.00" deep with an 8.28" flange and 19.7 in² of area. It is used as a heavily loaded short column where a deeper shape won't fit.
Is a W8 beam actually 8 inches deep?
Only approximately. The 13 W8 sections range from 7.89" (W8x10) to 9.00" (W8x67) in actual depth. Use the actual depth from the chart when checking clearances or detail dimensions, and use the weight per foot for tonnage.
How do I calculate the weight of a W8 beam?
Multiply the weight per foot by the length in feet. A W8x18 at 22 feet weighs 18 × 22 = 396 lb. For a whole job, sum the pieces and divide by 2,000 for short tons; the steel beam weight guide covers waste and connection allowances.