How to Read AISC Steel Tables — Complete Guide to Table 1-1

The AISC Steel Construction Manual Table 1-1 is the single most-referenced page in American structural steel design. Every W-shape beam and column check starts with the numbers on this table. Yet many engineers, particularly those early in their careers, use only the first few columns — depth, weight, Ix — and miss half the information that the table provides. This guide walks through every column in AISC Table 1-1, explains what each value means physically, and shows how to use it in LRFD and ASD design.

The layout of AISC Table 1-1

Table 1-1 is organised with W-shapes listed in order of decreasing weight per foot within each nominal depth group. The columns are grouped into four logical sections:

  1. Designation and weight — the shape name and mass properties
  2. Dimensions — actual measured dimensions of the cross-section
  3. Section properties — computed geometric properties for analysis and design
  4. Compactness criteria — slenderness limits for classification

Group 1: Designation and weight

Column Symbol What it tells you
Shape e.g. W27x84 Nominal depth (27 in) and weight per foot (84 lb/ft). The nominal depth is rounded; actual depth d is given in the dimensions columns.
A Area Cross-sectional area in in^2. Used for axial tension (Pn = Fy _ Ag), axial compression (Pn = Fcr _ Ag), and self-weight verification (A * 490 lb/ft^3 / 144 = lb/ft).

Group 2: Dimensions

These are the physical dimensions of the cross-section, measured to the nearest 0.001 inch for flange and web thickness. Every dimension has a specific design application:

Symbol Name Design application
d Actual depth Used in ALL flexural and shear calculations. The actual depth differs from the nominal depth (e.g., W27x84 has d = 26.7 in, not 27 in). Always use d, not the nominal depth.
bf Flange width Determines flange compactness (bf/2tf), bearing area for connections, and clearance for adjacent members. Wider flanges improve lateral stability.
tf Flange thickness Drives the plastic moment capacity Mp. Thicker flanges increase Zx and Zy. Also used in flange compactness check: bf/2tf <= lambda_pf.
tw Web thickness Critical for shear capacity (Vn = 0.6 _ Fy _ Aw * Cv). Thicker webs increase Vn and improve web compactness. Also used in block shear calculations for connections.
bf/2tf Flange slenderness Determines flange compactness per AISC Table B4.1b. Must be <= lambda_pf (0.38 * sqrt(E/Fy)) for compact flange. Non-compact flanges reduce Mn below Mp.
h/tw Web slenderness Determines web compactness. h is the clear distance between flanges minus the fillet radius: h = d - 2kdes. h/tw <= lambda_pw (3.76sqrt(E/Fy)) for compact web in flexure.
T Distance between fillets Used in bolt gage calculations and connection geometry. Also used in WT-shape designation when a W-shape is split into tees.
kdes Design fillet distance Distance from outer face of flange to the web toe of the fillet. Used to compute h = d - 2*kdes for web slenderness. Not the same as kdet (detailing dimension).

The kdes vs kdet distinction

This is a common point of confusion. kdes is the design dimension used in all strength calculations (web slenderness, shear buckling). kdet is the detailing dimension used for connection geometry (beam copes, stiffener fit-up). kdes is always larger than kdet because it includes the flange-to-web radius. Using kdet where kdes is required overestimates the web depth, leading to unconservative web slenderness calculations.

Group 3: Strong-axis section properties

These properties describe the section's resistance to bending about the strong (X) axis — the axis parallel to the flanges:

Symbol Property Units Formula / use
Ix Moment of inertia in^4 Deflection (delta = 5wL^4/(384EI)), flexural buckling (Fe = pi^2*E/(KL/r)^2), moment distribution in indeterminate frames
Sx Elastic section modulus in^3 Yield moment My = Fy * Sx. Used for ASD stress checks (fb = M/Sx <= Fb). Always smaller than Zx by the shape factor.
Zx Plastic section modulus in^3 Plastic moment Mp = Fy _ Zx. Used for LRFD flexural strength (phi_b _ Mn). Zx/Sx ratio (shape factor) is typically 1.10–1.16 for compact W-shapes.
rx Radius of gyration in rx = sqrt(Ix/A). Used for column slenderness KL/r about the strong axis. Larger rx means better strong-axis buckling resistance.

Group 4: Weak-axis section properties

The weak-axis (Y) properties are equally important but often overlooked until a column buckling check demands them:

Symbol Property Units Design significance
Iy Weak-axis moment of inertia in^4 Lateral-torsional buckling (LTB) uses Iy. Wider flanges dramatically increase Iy: a W14x90 (bf=14.5 in) has Iy=362 in^4 vs a W21x50 (bf=6.53 in) with Iy=24.9 in^4.
Sy Weak-axis elastic modulus in^3 Used for minor-axis bending stress checks (e.g., wind on column flange, crane rail eccentricity).
Zy Weak-axis plastic modulus in^3 Plastic moment capacity for minor-axis bending in LRFD combined loading checks (AISC H1 interaction equations).
ry Weak-axis radius of gyration in GOVERNS column buckling for unbraced columns. For a W12x65, rx=5.28 in but ry=3.02 in. The weak axis always controls unless the column is braced in the Y-direction.

Group 5: Torsional and warping properties

Symbol Property Design significance
J Torsional constant (in^4) Resistance to pure (St. Venant) torsion. Open sections like W-shapes have very low J — a W21x50 has J=1.14 in^4. Compare with HSS8x8x1/2 at J=75.8 in^4. W-shapes rely on warping restraint, not pure torsion.
Cw Warping constant (in^6) Resistance to warping torsion. Cw is used in LTB calculations (Fcr formula for elastic LTB region). Cw is proportional to Iy * (d - tf)^2 / 4 for doubly-symmetric I-shapes.
ho Distance between flange centroids ho = d - tf. Used in LTB calculations. A deeper section with the same flanges has a larger ho, increasing Cw and therefore LTB resistance.

Group 6: Compactness criteria

The rightmost columns of Table 1-1 give pre-computed slenderness ratios and the compactness limits from AISC Table B4.1b. These determine whether the section can develop its full plastic capacity or must be reduced for local buckling:

Flange compactness:
  bf/2tf  --  actual flange slenderness
  lambda_pf = 0.38 * sqrt(E/Fy)  --  compact limit (e.g., 9.15 for Fy=50 ksi)
  lambda_rf = 1.00 * sqrt(E/Fy)  --  non-compact limit (e.g., 24.1 for Fy=50 ksi)

  If bf/2tf <= lambda_pf  -->  Compact flange, Mp can be used
  If lambda_pf < bf/2tf <= lambda_rf  -->  Non-compact flange, Mn between Mp and My
  If bf/2tf > lambda_rf  -->  Slender flange, local buckling reduces Mn below My

Web compactness:
  h/tw  --  actual web slenderness
  lambda_pw = 3.76 * sqrt(E/Fy)  --  compact limit (e.g., 90.6)
  lambda_rw = 5.70 * sqrt(E/Fy)  --  non-compact limit (e.g., 137.3)

Practical example: reading a W18x50 line

Let us read across the complete W18x50 entry and interpret each value:

W18x50:  A=14.7 in^2
  d=18.0 in, bf=7.50 in, tf=0.570 in, tw=0.355 in
  bf/2tf=6.58, h/tw=45.2
  Ix=800 in^4, Sx=88.9 in^3, Zx=101 in^3, rx=7.38 in
  Iy=40.1 in^4, Sy=10.7 in^3, Zy=16.5 in^3, ry=1.65 in
  J=1.24 in^4, Cw=1720 in^6, ho=17.4 in

Interpretation for design:

How to quickly select a beam using Table 1-1

When sizing a beam from scratch, select the required Zx (plastic modulus) from the factored moment demand:

Zx,req = Mu / (phi_b * Fy) = Mu * 12 / (0.90 * 50)  for ksi units

For Mu = 250 kip-ft: Zx,req = 250*12/(45) = 66.7 in^3
  --> Scan Table 1-1 Zx column for sections with Zx > 66.7:
      W16x40  Zx=73.0 in^3, W18x35 Zx=66.5 in^3 (marginal), W21x44 Zx=95.4 in^3

For deflection-controlled beams, scan the Ix column instead:
  Delta_max = 5wL^4/(384*E*I) --> Ix,req = 5wL^4/(384*E*Delta_allow)
  Select a section with Ix > Ix,req, then verify strength.

For columns, sort by ry (or rx, whichever controls) and select
sections where KL/r is below the inelastic buckling threshold:
  KL/r <= 4.71 * sqrt(E/Fy) = 113 for Fy=50 ksi

The table is organised to make this selection efficient. Sections are grouped by nominal depth, then sorted by decreasing weight within each group. This means that within a depth group, the heavier sections (more capacity) appear first.

ASD vs LRFD: which column values do I use?

Table 1-1 provides section properties that are independent of the design methodology (ASD or LRFD). The properties d, bf, tf, tw, A, Ix, Sx, Zx, rx, ry, J, Cw, ho are all geometric — they do not change between ASD and LRFD. What changes is how you use them:

The same Zx = 101 in^3 gives:

Always confirm which methodology applies to your project. AISC 360-22 makes LRFD the default in Chapter B, but both methods are permitted.

How properties change across section families

Engineers often need to compare sections across different depth groups or flange widths. Table 1-1 makes this possible at a glance:

These trends are visible by scanning across the table columns. When faced with an LTB-governed beam, scan to the right (Iy, Cw) not just the left (Ix, Zx).

Common mistakes when reading AISC Table 1-1

Try the calculator

The Steel Calculator Section Properties Database provides instant access to the complete AISC Table 1-1 with all dimensional and section properties for every W, HSS, C, L, and WT shape. Search by designation, compare sections side-by-side, and view properties in both imperial and metric units. Every value is independently verified against the AISC Manual 15th Edition.

For beam and column capacity checks using these properties, the Beam Capacity Calculator and Column Capacity Calculator integrate section selection directly from the database. Browse the database here.