Section Properties Calculator

Calculate complete cross-sectional properties for structural steel sections. Get area, moment of inertia, torsion constant, section modulus, and centroid location for I-beams, channels, angles, and more.

Section Properties Explained

Area (A)

The cross-sectional area in mm² or in². Used to calculate axial stress (σ = P/A) and self-weight. For hollow sections, this is the material area only.

Moment of Inertia (I_yy, I_zz)

The second moment of area about the principal axes, in mm⁴ or in⁴. I_zz is typically the strong axis (resisting bending about the horizontal), while I_yy is the weak axis. These determine bending stiffness and stress distribution.

Torsion Constant (J)

The St. Venant torsion constant in mm⁴ or in⁴. For closed sections (pipes, RHS), J is large and the section resists twisting well. For open sections (I-beams, channels, angles), J is much smaller—these sections are prone to torsional buckling.

Section Modulus (S_yy, S_zz)

The elastic section modulus in mm³ or in³, calculated as I/c where c is the distance to the extreme fibre. Used to find bending stress: σ = M/S. A larger section modulus means lower stress for the same moment.

Centroid (C_y, C_z)

The location of the geometric centre of the section. For symmetric sections like I-beams and rectangles, the centroid is at the geometric centre. For asymmetric sections like channels and angles, the centroid shifts toward the heavier portion.

Supported Section Types

Notes on Accuracy

This calculator uses simplified formulas that ignore fillet radii and corner radii. For standard steel sections, the actual properties (available in manufacturer tables) are slightly higher due to the additional material in fillets. The difference is typically 2-5%.

For precise values, consult published section tables (AISC, British Steel, ArcelorMittal, etc.) or use our full structural analysis tool which includes a comprehensive library of standard sections with accurate properties.

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