Round steel tubes sizes, dimensions and section properties are given in the following chart per Steel Construction Manual.

Round steel tubes are usually manufactured to meet ASTM A500 grade B (Fy = 42 ksi) or grade C (Fy = 46 ksi). Round steel tubes have an round and uniform wall thickness, except at the weld seam(s). Round steel tubes are designated by "HSS", nominal outside diameter (in.), and wall thickness. HSS 6.000 x 0.500 is nominally 6 in. in diameter with a 1/2 in. nominal wall thickness.

Moment of inertia, elastic section modulus, radius of gyration, torsional moment of inertia and plastic section modulus values are given by the following calculator for the selected round steel tube size.


HSS Outside Dimension HSS Wall Thickness


HSS Steel Tube Sizes and Dimensions
Parameter Symbol Value Unit
Shape --- --- ---
Design wall thickness* tdes --- in
Nominal weight w --- lb/ft
Area A --- in2
D/t --- --- ---
Second moment of area I --- in4
Elastic section modulus S --- in3
Radius of gyration r --- in
Plastic section modulus Z --- in3
Polar moment of area J --- in4
Torsional constant for HSS shapes C --- in3

Note: Use dot "." as decimal separator.
Note *:The design wall thickness t, shall be used in calculations involving the wall thickness of hollow structural sections (HSS) per Steel Construction Manual Section B3.12.


Second Moment of Area: The capacity of a cross-section to resist bending.

Radius of Gyration (Area): The distance from an axis at which the area of a body may be assumed to be concentrated and the second moment area of this configuration equal to the second moment area of the actual body about the same axis.

Section Modulus: The moment of inertia of the area of the cross section of a structural member divided by the distance from the center of gravity to the farthest point of the section; a measure of the flexural strength of the beam.