I Beam Sizes — Complete W-Shape Dimension and Weight Chart

When people say "I beam," they almost always mean a W-shape (wide-flange) section — the standard steel beam profile used in American construction since the 1940s. The term "I beam" is colloquial and does not appear in the AISC Steel Construction Manual. The correct designation is W-shape, and this page gives you the dimensions, weights, and properties you need to identify, order, or estimate the right beam for your project.

How to read a W designation: W12x26 means a W-shape with a 12-inch nominal depth that weighs 26 pounds per foot. The "12" is a label, not an exact measurement — the actual depth of a W12x26 is 12.22 inches. The weight per foot is accurate and is the number you use for ordering and estimating total steel weight.

Quick access: Calculate beam capacity | Full section properties database | Steel weight calculator

Top 20 Most Popular I Beam Sizes (W-Shapes)

The 20 most commonly specified W-shapes in North American construction, covering the full range from light residential beams (W8) to heavy industrial girders (W36). All values from AISC Steel Construction Manual, 16th Edition, Table 1-1. Steel grade: ASTM A992 (Fy = 50 ksi, Fu = 65 ksi).

Source: AISC Steel Construction Manual, 16th Edition. All sections ASTM A992 steel (Fy = 50 ksi, Fu = 65 ksi). Values are nominal — verify with current edition before procurement.

What Is an I Beam?

An "I beam" gets its name from its cross-sectional shape: two horizontal flanges connected by a vertical web, forming the letter I when viewed from the end.

        Flange
    _______________
|             |    --- Flange thickness (tf)
|_____________|
      | |           --- Web thickness (tw)
      | |
      | |           --- Depth (d)
      | |
______|_|______
|             |    --- Flange thickness (tf)
|_____________|
     Flange
<----------->
 Flange width (bf)

The flanges (top and bottom) resist bending. The wider and thicker the flanges, the more bending strength the beam has. The web (the vertical plate in the middle) resists shear and keeps the two flanges apart. Together, this I-shaped profile is the most structurally efficient shape for carrying loads across a span — which is why it dominates steel construction worldwide.

In US practice, the I-shaped profile comes in three main types:

• W-shape (Wide-Flange) — By far the most common. Flanges are roughly as wide as they are thick relative to the web, with flat inner faces. This is what 99% of people mean when they say "I beam."
• S-shape (American Standard) — Older profile with narrower, tapered (sloped) inner flange faces. Used for crane rails, monorails, and legacy structures. Less common in new construction.
• HP-shape (H-Pile) — Heavier web and flanges, designed to be driven into the ground as bearing piles. The flanges and web are nearly the same thickness.

W-Shape vs S-Shape vs HP-Shape Comparison

Understanding the difference between these three I-shaped sections matters because they are not interchangeable. Each has a specific purpose and a different dimensional profile.

If you are ordering steel for a building frame, you want W-shapes. If an engineer calls out an S-shape or HP-shape on your drawings, there is a specific reason — do not substitute without approval.

How to Read Beam Designations

Steel beam designations follow a consistent pattern. Once you understand it, you can read any beam size at a glance.

W-Shape Designation: W [depth] x [weight]

Example: W12x26

• W = Wide-flange shape
• 12 = Nominal depth group (approximately 12 inches)
• 26 = Weight per linear foot (26 lb/ft)

Key facts about the depth number: it is a nominal (approximate) label, not an exact dimension. The W12 series includes sections ranging from W12x14 (actual depth 11.91 in) to W12x336 (actual depth 16.95 in). The "12" comes from the approximate depth of the lighter sections in the group. For detailing and connection design, always look up the actual depth.

Key facts about the weight number: this is the exact weight per linear foot used for estimating total steel weight. If you need 40 feet of W12x26, the beam weighs 26 x 40 = 1,040 lb (just over half a ton).

S-Shape Designation: S [depth] x [weight]

Example: S12x31.8

• S = American Standard shape
• 12 = Nominal depth (approximately 12 inches)
• 31.8 = Weight per linear foot (31.8 lb/ft)

S-shapes have tapered inner flange faces (about 16.7% slope or approximately 2 inches of slope per 12 inches of flange). This taper means standard clip angles and end plates do not sit flat against the flange — special detailing is required. S-shapes are most commonly specified for crane rails and monorail beams where the tapered flange helps center the wheel load.

HP-Shape Designation: HP [depth] x [weight]

Example: HP12x53

• HP = H-Pile (bearing pile shape)
• 12 = Nominal depth (approximately 12 inches)
• 53 = Weight per linear foot (53 lb/ft)

HP-shapes have a nearly square cross-section (flange width is close to the depth) with thick webs and flanges. They are designed to be driven into soil as deep foundation elements. The heavy, uniform thickness helps them withstand driving forces without buckling or damaging the web. HP-shapes are also used in retaining walls (soldier piles) and braced excavations.

Most Popular I Beams by Application

Selecting the right beam size depends on the span, the load, and the application. Below are the most commonly specified W-shapes organized by building type. These are starting points for preliminary sizing — final selection requires structural calculation per AISC 360-22.

Residential Construction

Residential steel beams typically span 10 to 25 feet and carry floor or roof loads for single-family homes, garages, and additions. Lighter W-shapes are standard here.

Commercial Construction

Office buildings, retail spaces, and multi-story structures use medium-weight W-shapes. Spans range from 20 to 40 feet with heavier floor loads (partitions, mechanical equipment).

Industrial and Heavy Construction

Warehouses, manufacturing facilities, bridges, and heavy industrial structures use the deepest and heaviest W-shapes. Spans can exceed 60 feet, and loads include cranes, heavy equipment, and material storage.

I Beam Weight Per Foot Chart

For quick weight estimation, this simplified table lists the most common W-shapes sorted by weight. Multiply the weight per foot by the total beam length (in feet) to get the approximate total weight. Add 3-5% for connections, plates, and waste.

Weight estimation example: A W18x50 beam spanning 30 feet weighs 50 x 30 = 1,500 lb (three-quarters of a ton). For a bay of four beams, total steel = 4 x 1,500 = 6,000 lb. Add 5% for connections = 6,300 lb.

Understanding the Key Dimensions

When you look at a W-shape in the AISC manual or on a steel supplier website, you will see these dimensional properties. Here is what each one means in plain language.

Depth (d) — The total height of the beam from the bottom of the lower flange to the top of the upper flange. This is the dimension that determines your floor-to-floor height and your minimum ceiling clearance. A W18x50 is 17.99 inches tall — you need at least 18 inches of depth in your floor or ceiling assembly.

Flange width (bf) — The width of the top or bottom flange, measured from outside edge to outside edge. Wider flanges provide more resistance to lateral-torsional buckling (the beam twisting sideways under load) and give more room for bolted connections. A W12x65 has 12-inch wide flanges — that is why it is much more stable laterally than a W12x26 with 6.5-inch flanges.

Web thickness (tw) — The thickness of the vertical plate connecting the two flanges. The web carries shear (the force that tries to slice the beam vertically at supports). Thinner webs are more weight-efficient but may require stiffener plates at concentrated loads and reactions.

Flange thickness (tf) — The thickness of each flange. Thicker flanges directly increase the beam's bending strength and stiffness. Flange thickness also determines how many bolt rows you can fit in a connection and whether the flange is classified as "compact" or "non-compact" for local buckling checks per AISC 360-22 Table B4.1b.

Moment of inertia (Ix) — A measure of the beam's resistance to bending (stiffness). Higher Ix means less deflection under the same load. Ix is the property that governs how much a beam sags or bounces. For a simply supported beam with a uniform load, deflection is inversely proportional to Ix — double the Ix, halve the deflection.

I Beam Sizes by Depth Range

W8 Series (Approximately 8 Inches Deep)

The W8 series is used for short-span beams, columns in low-rise buildings, and mezzanine framing. There are 13 sections ranging from W8x10 to W8x67.

W10 Series (Approximately 10 Inches Deep)

The W10 series spans the gap between light framing and medium commercial beams. There are 18 sections from W10x12 to W10x112.

W12 Series (Approximately 12 Inches Deep)

The W12 series is the most versatile depth range — it works as both beams and columns. There are 19 sections from W12x14 to W12x336. The heavier W12 shapes (W12x120 and above) are primarily columns in mid-rise buildings.

W14 Through W36 (Larger Depths)

W14 through W36 shapes are used for heavy beams, transfer girders, bridge stringers, and long-span applications. The table below shows the most popular sizes in each depth group.

Frequently Asked Questions

What is the difference between an I beam and a W beam?

"I beam" is a general term people use to describe any steel beam with an I-shaped cross-section. In the AISC system, the correct name for the standard I-shaped beam is W-shape (wide-flange). There are also S-shapes (American Standard, with tapered flanges) and HP-shapes (H-piles, with thick webs for foundation use). When someone says "I beam," they almost certainly mean a W-shape. If you call a steel supplier and ask for an "I beam," they will ask you to clarify which W-shape you need.

How do I know what size I beam I need?

Beam selection depends on three factors: the span (how far the beam runs between supports), the load (how much weight it carries), and the deflection limit (how much sag is acceptable). For a residential floor beam spanning 20 feet, a W12x26 or W12x40 is a common starting point. For a commercial office floor beam spanning 30 feet, a W18x50 is typical. But these are preliminary estimates only — the actual required size must be calculated by a structural engineer per AISC 360-22, considering moment capacity, shear capacity, deflection, lateral-torsional buckling, and serviceability limits. Use the beam capacity calculator to run a check for your specific loading.

What does the "x" mean in W12x26?

The "x" is read as "by" — W12x26 is spoken as "W twelve by twenty-six." It separates the nominal depth (12 inches) from the weight per linear foot (26 lb/ft). Every W-shape follows this pattern: the letter W, then the nominal depth, then x, then the weight.

Are I beam dimensions in the designation exact?

No. The depth in the designation is nominal — it is a grouping label, not an exact measurement. For example, the W12 group includes sections with actual depths ranging from 11.89 inches (W12x14) to 16.95 inches (W12x336). The "12" simply identifies the depth group. However, the weight per foot is accurate — a W12x26 does weigh 26 lb/ft. For connection detailing, clearance checks, and any dimension-critical work, always use the actual depth from the AISC manual or the section properties database, not the nominal designation.

How much does an I beam cost?

Steel pricing fluctuates with the market, but as of early 2026, structural steel (W-shapes) typically costs $0.80 to $1.50 per pound, depending on the section size, mill, and order quantity. A W12x26 spanning 20 feet weighs 520 lb and would cost approximately $400-$780 for the raw steel. Fabrication (cutting, drilling holes, welding connection plates, painting) typically doubles or triples the raw steel cost. Delivery, erection, and engineering are additional. Contact a local steel fabricator for a firm quote — prices vary significantly by region and market conditions.

What steel grade are standard I beams?

In the United States, the standard steel grade for W-shapes is ASTM A992, which has a minimum yield strength (Fy) of 50 ksi and a minimum tensile strength (Fu) of 65 ksi. A992 replaced A36 as the default grade for structural shapes in 2000. Some shapes are also available in A572 Grade 50 (very similar properties) or A36 (Fy = 36 ksi, for lighter and older shapes). For HP-shapes, ASTM A572 Grade 50 is the most common specification. Always confirm the steel grade with your supplier before ordering — the grade affects all structural capacity calculations per AISC 360-22.

Can I use a bigger beam instead of calculating the exact size?

You can, but it costs more and may cause other problems. Over-sizing a beam means you pay for steel you do not need, the beam is heavier to lift and erect (requiring larger equipment), and it takes up more vertical space (reducing ceiling height or increasing floor-to-floor height). For small residential projects, many contractors size beams conservatively. But for anything beyond a simple residential beam, a proper structural calculation is worth the cost — it typically saves more in material and erection costs than the engineering fee. Use the beam capacity calculator as a starting point.

Run This Calculation

• Beam Capacity Calculator — moment, shear, and LTB checks per AISC 360-22 for any W-shape
• Steel Weight Calculator — total beam weight by length and section
• Section Properties Database — full Ix, Sx, Zx, rx, ry for all 148 W-shapes

Related References

• Steel Beam Sizes — Full Properties Chart — all 148 AISC W-shapes with Sx, Zx, rx, ry
• Beam Formulas — Moment, Shear and Deflection Equations
• Steel Beam Span Guide — W-Shape Span Ranges by Depth
• Beam Design Guide — Step-by-Step AISC 360
• Steel Grades and Material Properties
• Section Comparison Tool
• Disclaimer (educational use only)

Disclaimer (educational use only)

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