Know your section. See its axes.
Area, centroidal second moments, section modulus and optional mass for four simple cross-sections.
01 · Your inputs
Ideal geometry only: sharp corners and uniform wall thickness. This tool does not check structural capacity, buckling or torsional performance.
02 · Your result
Ready to calculate
Inputs stay in this tab. Nothing is uploaded or saved automatically.
Understand the calculation
Formula & assumptions
Circle: A = πD²/4; Ix = Iy = πD⁴/64
Hollow: outside section minus concentric inside section
Zx = Ix/(h/2); Zy = Iy/(b/2); r = √(I/A)
Mass (kg) = A (mm²) × 10⁻⁶ × length (m) × density (kg/m³)
The diagram uses the same geometry as the calculation. The horizontal x axis and vertical y axis pass through the centroid. Rotating a rectangle changes which second moment applies to your bending direction.
Sources & limitations
These are second moments of area (mm⁴), not mass moments of inertia (kg·m²). Ix + Iy is not a general substitute for a non-circular torsion constant. Real hollow sections have corner radii not modelled here.
Alkoc Labs calculation engine v0.4.0. Educational and preliminary engineering use; independently verify inputs and results for consequential decisions. Display precision is not measurement uncertainty.
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