Rectangular & Square Tubing Section Properties Chart (HSS/RHS) — Weights, Ix/Iy, Zx/Zy, J, r

In structural engineering and fabrication, rectangular steel tubing (also called HSS or RHS) and square tubing (SHS) are among the most versatile members used in frames, beams, columns, and trusses. This blog post gives you a full square tubing section properties chart, including weights, moment of inertia (Ix, Iy), section modulus (Zx, Zy), torsion constants, radius of gyration, and more. Use this as a reference when selecting the right structural steel tubing for strength, bending, buckling, and torsional requirements.

Box Section vs. Square Hollow Section (SHS) vs. Rectangular Hollow Section (RHS)

• HSS = Hollow Structural Section (generic term; includes round, square, and rectangular shapes)
• RHS = Rectangular Hollow Section (when the cross-section is rectangular: height ≠ width)
• SHS = Square Hollow Section (height = width)
• All are types of steel box tubing or steel tube profiles used widely in structural applications.

A rectangular steel tube is often denoted as h × b × t, where h = height, b = width, and t = wall thickness (design wall). For example, “24×12×3/4” means 24 in height, 12 in width, 0.75 in wall thickness.

ASTM A500 (Grade B/C) Steel Box Tube: Dimensions, Wall Thickness, and Uses

Most structural rectangular tubing is manufactured to ASTM A500 (Grade B or C). These rectangular box steel members come in standard nominal sizes and wall thicknesses. They are often used in building frames, trusses, gantries, supports, and architectural structures.

Wall thickness (t) is critical: it directly affects weight per foot, section modulus, moment of inertia, torsional stiffness, and resistance to local buckling.

For ASTM A500, see:

Below is a sample table of common rectangular tubing sizes and their weight per foot (lb/ft). This gives you a sense of how much weight each tubing contributes to a structure.

You can see that as wall thickness decreases, weight per foot drops significantly, but that also reduces bending and torsional strength.

A critical factor in beam design is how a cross-section resists bending. That is captured by the second moment of area (also called moment of inertia, I) and the section modulus, Z. Radius of gyration ris used in buckling calculations.

Understanding the Radius of Gyration (r)

The radius of gyration (r) is a key geometric property used in column buckling calculations for rectangular and square steel tubing (HSS/RHS/SHS). It represents how the cross-section’s area is distributed around its centroidal axis — in simpler terms, how far the material is spread from the center.
Mathematically, it’s defined as:

where:

I= moment of inertia (in⁴) about a given axis
A= cross-sectional area (in²)
There are two values:
rₓ — radius of gyration about the strong (x-x) axis
rᵧ — radius of gyration about the weak (y-y) axis

A larger radius of gyration means the section’s area is distributed farther from its centroid, which increases buckling resistance. When comparing rectangular HSS for columns or compression members, engineers often use the slenderness ratio (KL/r) — where K is the effective length factor and L is the unsupported length.
For example:

A 24×12×0.75 HSS has r_x=8.52in and r_y=5.79in, making it very stiff about its major axis.
A 10×6×0.5 HSS has smaller radii, meaning it will buckle more easily under axial compression unless braced.

In short, the radius of gyration helps you predict how resistant a rectangular or square tubing section will be to column buckling, complementing Ix, Zx, and J in a full structural analysis.

• Area (A): cross-sectional area in in²
• Ix, Iy: second moment of area about the x-x and y-y axes
• Zx, Zy (or Sx, Sy): elastic section modulus = I/(c), where cis the distance from neutral axis to extreme fiber
•  r: radius of gyration = √(I/A)
   • Typically, x-x axis is the strong axis (bending about the major axis), and y-y axis is the weak axis.

Here is a sample excerpt from a detailed table:

24×12×0.75 HSS: Ix/Iy and Zx/Zy Reference

•I_x=3650" " 〖"in" 〗^4, I_y=1240" " 〖"in" 〗^4
•Z_x=304" " 〖"in" 〗^3, Z_y=207" " 〖"in" 〗^3

This implies it is very much stronger bending about the x-x axis than the y-y axis.

20×8×1/2 Rectangular Tube: Ix, Iy, and Z for Bending Stiffness

For the 20×8×0.5 section:

•I_x≈1270" " 〖"in" 〗^4, I_y≈300" " 〖"in" 〗^4
•Z_x≈127" " 〖"in" 〗^3, Z_y≈75" " 〖"in" 〗^3

 Use Z_xfor bending in the strong direction; Z_ywhen bending about the weak axis is critical.

Rectangular hollow sections do not have a simple polar moment of inertia like solid sections. Instead we use torsional constant (J) and warping constant (C) for torsional stiffness and behavior.

• J: torsional constant, describes resistance to torsion (twisting)
• C: warping constant, relevant in open or noncompact sections

Excerpt from a sample section properties table:

From the extended table:

•  J≈74.1" " 〖"in" 〗^4for the 12x10x1/2 (similar logic)
•Use J in torsional stiffness calculations: θ=TL/GJ, where Gis shear modulus.

When to Prioritize J vs. Ix/Iy in Frame and Beam Design

•If twisting loads are significant (e.g. shaft, torque frame member), J becomes critical
•If only bending loads dominate, Ix, Iy, Zx, Zy govern beam selection
•Use a combined interaction in complex members: check bending, shear, torsion together.

Thus, choose t to balance weight, bending, torsion, and local buckling constraints.

For coating cost estimates or corrosion allowance, the surface area per foot is relevant (neglecting ends). Use:

"Perimeter"=2(h+b-2t)"(subtract thickness offset)"
"Surface area per foot (ft²/ft)"="Perimeter (in)" /12

Sample from the table:
24×12×0.75 section: ≈ 5.79 ft² per foot
20×12×0.75: ≈ 5.12 ft²/ft
16×12×0.75: 4.45 ft²/ft
Smaller sections drop below ~2 ft²/ft
This is helpful when budgeting painting, galvanization, or corrosion coatings.

•Use Zx = elastic section modulus for bending stress: σ=M/Z
•Use Ix for deflection and stiffness: δ∝L^3/(EI)
•Higher Zx for strength, higher Ix for stiffness

Often designers pick a tube where Z_x/"weight" is maximized — best bending strength per mass.

Long-Span Frames: 24×12 vs. 20×12 vs. 16×12 — Which HSS Wins?

Compare weight and Zx:

• 24×12×0.75: 171 lb/ft, Zx = 304
• 20×12×0.75: 150.75 lb/ft, Zx = 232
• 16×12×0.75: 130.33 lb/ft, Zx = 134

24×12 gives higher strength but heavier. 16×12 might be more efficient for moderate spans. Always check deflection, strength, buckling, and torsion together.

What’s the Difference Between HSS, RHS, SHS, and “Steel Box Tube”?

•HSS is generic (hollow structural section)
•RHS is rectangular hollow section
•SHS is square hollow section
•Box tube / steel box section colloquial term used in fabrication

How Do I Convert Between Section Modulus (Z) and Moment of Inertia (I)?

 •Z=I/c, where cis the distance from neutral axis to extreme fiber
•For symmetric rectangular tubes: c=h/2or b/2

What Are Typical Applications for 10×8, 12×6, and 8×4 Rectangular Tubing?

•10×8×5/8: medium-sized frames, columns in low-rise structures
•12×6×1/2: support beams, small mezzanines
•8×4×5/8: light trusses, bracing, railing supports

Selecting rectangular and square steel tubing for structural or mechanical systems demands more than just choosing a size. You need to balance weight, bending strength (Zx, Zy), stiffness (Ix, Iy), torsional rigidity (J), and local buckling limits (b/t, h/t). The tables above can help you make informed decisions.