How AISC W shapes are designated

American structural shapes follow the naming of ASTM A6/A6M and the AISC Manual: a letter for the shape family, then the nominal depth and the weight per foot, separated by an "x". W10x49 is a wide flange shape about 10 inches deep that weighs 49 pounds per foot. The depth is nominal: the W10 family runs from 9.87 to 11.4 inches, because the heavier members of a family are rolled with the same inner rolls and thicker flanges.

The families

• W (wide flange): parallel flanges, the workhorse for beams and columns, W4 to W44. The European counterparts are IPE (narrow) and HEA/HEB/HEM (wide), the British ones UB and UC.
• S (American standard beam): tapered flanges, the old "I beam". Equivalent to IPN in Europe and joists in the UK.
• HP (bearing pile): W-like shape with flange and web of equal thickness, like the European HP and the British UBP.
• M (miscellaneous): light shapes that fit none of the above.
• C and MC (channels): American standard and miscellaneous channels with tapered flanges, C3 to C15 and MC3 to MC18. UPN and PFC are the metric cousins.
• L (angles): L4x4x1/2 gives both leg lengths and the thickness, like L 100 x 100 x 10 in Europe.
• WT, ST, MT (tees): cut from W, S and M shapes. WT5x24.5 is half a W10x49.
• HSS (hollow structural sections): HSS6x4x1/4 is a rectangular tube 6 by 4 inches with a 1/4 inch nominal wall; HSS6.625x0.280 is a round one by outside diameter and wall. The design wall thickness is 0.93 times the nominal for A500 tubes, which the AISC tables account for.
• PIPE: Pipe 4 Std, X-Strong and XX-Strong by nominal size and weight class.
• 2L: double angles, back to back, with the gap given in the designation (2L4x4x1/2x3/8).

Metric designations

The same shapes have an SI name in the AISC tables: nominal depth in millimetres and mass in kilograms per metre. W10x49 is W250x73, W14x90 is W360x134, C10x15.3 is C250x22.8. The metric name is a conversion, not a different product: the section is rolled to the imperial dimensions. Canadian CISC sections use the same metric designations with a hard metric rolling programme.

Depth, weight and what they tell you

• Within a family the weight per foot ranks the sections by size: a W10x49 has thicker flanges than a W10x33 and a larger section modulus, at the same nominal depth.
• Two members of different families can share a weight: W12x40 and W10x39 differ in depth and width, not in cost per foot. The deeper one is stiffer, the wider one is better as a column.
• Columns are usually picked among the W8, W10, W12 and W14 families whose width is close to the depth (W14x90 is 14.0 x 14.5 inches), beams among the deeper families (W16 to W36) with narrow flanges.
• The AISC tables also give the "det" dimensions rounded to 1/16 and 1/8 inch for detailing, and the k distance from the outer flange face to the end of the web fillet.

Finding the European or British equivalent

There is no exact match between the imperial and metric families, and the steel grades differ too (A992 at 50 ksi against S355 at 355 MPa). The practical way is to match the governing property: moment of inertia for a beam governed by deflection, section modulus for strength, radius of gyration for a column. The Equivalent Finder in Steel Profiles does exactly that: it ranks the sections of another standard by the weighted difference in weight, area, I_x and I_y, within the same shape family, and shows the two sections side by side in their own units. See also the steel grade equivalents.

AISC 14th and 16th edition

The 16th edition of the AISC Manual (2023) updated the shape database: new W, HSS and pipe sizes, discontinued ones removed, and a few corrected properties. Both the 14th and the 16th edition tables are in the app, in US and SI units, so an existing design can be checked against the edition it was made with.