Tube (HSS) properties
Section properties for square hollow structural sections (HSS): weight, area, moment of inertia, and section modulus. Closed tube sections are stiff, efficient in bending both ways, and highly resistant to twisting.
Square HSS (ASTM A500), design wall
| Size | Weight (lb/ft) | Area (in²) | Ix (in⁴) | Sx (in³) |
|---|---|---|---|---|
| HSS2x2x1/4 | 5.41 | 1.51 | 0.747 | 0.747 |
| HSS3x3x1/4 | 8.81 | 2.44 | 3.02 | 2.01 |
| HSS3x3x3/8 | 12.17 | 3.39 | 3.78 | 2.52 |
| HSS4x4x1/4 | 12.21 | 3.37 | 7.80 | 3.90 |
| HSS4x4x3/8 | 17.27 | 4.78 | 10.3 | 5.13 |
| HSS5x5x1/4 | 15.62 | 4.30 | 16.0 | 6.39 |
| HSS6x6x1/4 | 19.02 | 5.24 | 28.6 | 9.54 |
| HSS6x6x3/8 | 27.48 | 7.58 | 39.5 | 13.2 |
| HSS8x8x1/4 | 25.82 | 7.10 | 70.7 | 17.7 |
| HSS8x8x3/8 | 37.69 | 10.4 | 100 | 25.1 |
An HSS is named by its outside dimensions and wall thickness, so HSS4x4x1/4 is a 4 inch square tube with a 1/4 inch nominal wall. Values use the AISC design wall, about 93 percent of nominal. Because the section is closed and symmetric, a square tube is equally strong both ways and far stiffer in torsion than an open shape, which is why tubes are favored for columns and posts.
Comparing against beams, channels, or angles?
See the Steel Beam Properties Chart for wide-flange shapes.
Why closed tubes resist twisting
A closed section carries torsion as a continuous shear flow all the way around the wall, which is enormously more effective than the open path in a channel or angle. That is why a square or round tube can be hundreds of times stiffer in torsion than an open shape of the same weight, making tubes the natural choice for posts, frames, and anything that must resist twisting.
Square tube as a column
For a column the ideal section is stiff in every direction, and a square tube delivers exactly that, with equal moment of inertia both ways and no weak axis to buckle about first. Combined with good torsional rigidity and a clean appearance, this makes HSS the common choice for building columns, railings, and equipment frames.
FAQ
What does HSS4x4x1/4 mean?
A square hollow structural section 4 inches on a side with a 1/4 inch nominal wall thickness. Design calculations use about 93 percent of the nominal wall.
Why is square tube good for columns?
It has equal stiffness in both directions, so there is no weak axis to buckle about, plus high torsional rigidity, making it efficient and stable as a column.
Is tube stronger than angle or channel?
In torsion and as a column, yes, by a wide margin, because the closed section resists twisting and buckling far better than open shapes of similar weight.