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Section Properties Calculator

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Section Properties Calculator
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Features & Capabilities

Standard Shape Library

Rectangle, circle, hollow circle, I-beam, channel, angle, T-section, and HSS tube with all dimensions parameterized.

Custom Built-Up Sections

Define custom sections from multiple rectangular plate elements. The parallel axis theorem is applied automatically to compute composite properties.

Complete Property Output

Calculates area, centroid location, Ix, Iy, Sx, Sy, rx, ry, Zx (plastic section modulus), and J (torsion constant for simple shapes).

Visual Diagram

Cross-section diagram with centroid and neutral axis location clearly marked for verification.

Parallel Axis Breakdown

Shows each component's local moment of inertia and transfer (Ad²) contribution so you can verify the composite calculation step by step.

Frequently Asked Questions

The parallel axis theorem (also called the transfer formula) calculates the moment of inertia of a shape about any axis parallel to its centroidal axis: I = I_centroid + A*d^2, where d is the distance between the two parallel axes. This is essential for built-up sections where each plate element has its own centroid offset from the composite section centroid.
The elastic section modulus S = I/c gives the stress at the extreme fiber when the section is in the elastic range. The plastic section modulus Z is the first moment of area about the plastic neutral axis (equal-area axis). Z is always larger than S. AISC LRFD uses Z for compact sections because the full plastic moment Mp = Fy*Z represents the true bending capacity.
AISC tabulated properties account for fillet radii at the web-flange junction, which add material and increase the moment of inertia slightly. A rectangular plate model of the same W-shape ignores the fillets and will underestimate I by 1-3%. For final design, use the AISC tabulated values. This calculator is most useful for custom built-up sections not found in the manual.
Disclaimer: This calculator provides section properties based on idealized geometry. For design purposes, verify results against AISC Steel Construction Manual tabulated values for standard shapes. Built-up section properties should be checked by a licensed structural engineer for use in final design.

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