Structural Engineering

Cross-Section Properties

Calculate geometric properties (area, second moment of area, section modulus) for common structural cross-sections.

Units:
in LinkedIn
💡The section modulus W = I/c determines bending strength. The radius of gyration i = √(I/A) determines buckling behaviour. For equal bending stiffness, a hollow section uses significantly less material than a solid section — important for weight-critical designs.
I_rectangle = b×h³/12 | I_circle = π×d⁴/64 | W = I/c | i = √(I/A)
ƒ Calculation module
Input
Cross-section type iSelect the cross-section shape.
Dimension 1 (width b / outer D) iRectangle: width b. Circle: outer diameter D. I-section: flange width b.
mm
Dimension 2 (height h / outer H) iRectangle: height h. Hollow: outer height H. I-section: total height H.
mm
Wall thickness t (hollow) / flange tf (I) iWall thickness for hollow sections. Flange thickness for I-sections. Leave 0 for solid sections.
mm
Web thickness tw (I-section only) iWeb thickness for I-sections in mm. Only used for I-section type.
mm
Result
Cross-section area A [cm²]
Second moment I_y (strong axis) [cm⁴]
Section modulus W_y [cm³]
Second moment I_z (weak axis) [cm⁴]
Radius of gyration i_y [cm]
Mass per metre (steel) [kg/m]
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