Engineering calculator

Composite Section Studio

Build a cross-section from rectangles, assign materials, and see the geometry and calculated properties update as you edit. Your inputs are kept in this browser.

1 · Materials

Define each material once. Reuse it for any rectangle.

2 · Cross-section rectangles

Enter opposite corners in millimetres. Coordinates may be negative.

3 · Neutral axis

Reference axis for Iₓ and EI. Enter its y-position in millimetres (may be negative).

Cross-section preview

Live geometry · equal x/y scale

0 rectangles

Dashed red line: neutral axis (reference axis for EI, adjustable). Dashed blue line: y-axis (x = 0). Overlapping rectangles are drawn as entered and are counted individually in the calculations.

Calculated properties

Recalculated immediately after each edit.

Bending stiffness per unit width
—
N·mm (EI ÷ overall x-span)
Mass per unit area
—
kg/m²
Total EI
—
N·mm² · reference axis y = 0
Overall x-span
—
mm
Add a rectangle to begin.

Material breakdown

Area and mass contribution by material.

Calculation notes

For each rectangle, the calculator follows your Python logic: A = |x₂ − x₁|·|y₂ − y₁| and Iₓ = width·(y_high³ − y_low³)/3 about the neutral axis y = y₀ (default 0, adjustable). EI is the sum of E·Iₓ across materials. Mass is calculated from density and rectangle area.

Per-unit-width convention: this interface reports EI divided by the total overall x-span of the section. Mass per unit area is total mass per unit length divided by that same span. For non-uniform-width sections, overlaps, or a different engineering definition of “per unit width,” verify that this convention matches your design standard.