Steel Beam Sizes

Quick Answer

W-Shape Wide Flange Beam Dimensions

Weights are exact and dimensions are nominal — the weight is what the shape name states, and the dimensions are the standard's nominal values, so both columns can be relied on for take-off, handling and shipping calculations.

Section properties are deliberately absent. Moment of inertia, section modulus and radius of gyration depend on the fillets between web and flange, which the nominal dimensions do not describe. Computing them from the dimensions above gives values 2–3% low. Take those values from the AISC Shapes Database for any design work — the section properties chart explains the difference.

The area column is derived from the stated weight, so it includes the fillets that the dimensions omit — which is why it is a useful cross-check rather than a restatement. Rolling tolerances mean a delivered beam is within a few percent of the nominal weight, not exactly on it.

How to Read a W-Shape Designation

W means wide flange — the shape whose flanges are nearly parallel, as opposed to the older S-shape (American Standard beam) whose flanges taper. The first number is the nominal depth in inches and the second is the weight in pounds per foot.

The depth is nominal, not exact: W14 shapes range from 13.91 to 14.16 in depending on weight, and all of them are called W14. That is why a W14×26 and a W14×90 have the same nominal depth but completely different capacity — the heavier shape has a thicker web and much wider, thicker flanges.

Because the name gives weight directly, a beam take-off is trivial: length in feet times the number in the name. A 30 ft W14×26 weighs 780 lb. That is the reason the naming convention exists.

Depth and Weight Are Independent Choices

Two design constraints usually drive the selection, and they pull in different directions. The depth is often set by the available construction depth — a floor zone, a header above an opening, a crane clearance. The required capacity is set by the loads.

The design problem is to find the lightest shape of the available depth that carries the loads. Going heavier at the same nominal depth increases both the flange size and the web thickness, which raises the moment of inertia substantially — a W14×90 carries roughly three and a half times the moment of a W14×26 despite being the same nominal depth.

Where depth is not constrained, a deeper lighter beam almost always wins on weight, because stiffness goes with the cube of depth. A W21×44 is about the same weight per foot as a W14×43 but considerably stiffer, which is why long spans use deep shapes and short ones use shallow heavy shapes.

Frequently Asked Questions

What does W14×26 mean?

A wide flange beam 14 inches deep weighing 26 pounds per foot. The first number is nominal depth and the second is weight, not flange width. The actual depth is 13.91 in — W14 shapes range from 13.91 to about 14.16 in and are all called W14.

How much does a steel beam weigh?

The weight per foot is the second number in the designation, so a W14×26 weighs 26 lb/ft or 38.7 kg/m. Multiply by the length: a 30 ft beam is 780 lb. Delivered weight is within a few percent because of rolling tolerance, usually slightly under nominal.

Where do I find the moment of inertia of a W-shape?

From the AISC Shapes Database or the equivalent national section property table, not from the nominal dimensions. The fillets between web and flange add 2–3% that the dimensions do not describe, so a value computed from depth, flange width and thicknesses comes out low.

What is the difference between a W-shape and an S-shape?

W-shapes have essentially parallel flange faces; S-shapes (American Standard beams) have tapered flanges and are the older series. W-shapes are more efficient because a parallel flange is easier to bolt to and gives a larger contact area for a connection plate. S-shapes are largely obsolete but still appear in older structures.

How do I choose a beam size?

Start from the depth the construction allows, then find the lightest shape of about that depth that satisfies both the strength and the deflection limits — deflection often governs for floors. Use the published load tables or the AISC Manual; a beam selected on strength alone frequently fails the L/360 deflection limit.

Related

• Section Properties Chart
• Steel Plate Sizes
• ASTM A992 Beam Steel
• ASTM A36 Steel Properties
• Beam Deflection Calculator
• Column Buckling Calculator

Value Sources

References and calculation methods used for this page are listed below. Numbered markers connect table columns where present. A reference listing does not itself establish that every value has been independently checked.

Data Sources

Verification scope

No page-specific independent source review is recorded here. The listed references and formulas explain the basis of the compilation; automated consistency checks do not verify the original sources or establish product conformity.

Derived values — the following values on this page are calculated, not taken directly from the standard:

Weights are exact as stated in the shape designation and dimensions are nominal. Section properties — I, S, r, Z — are not given, because they depend on fillets the nominal dimensions do not describe; take them from the AISC Shapes Database. Rolling tolerances mean delivered weight differs from nominal by a few percent.

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