Free Section Modulus Calculator
Compute the elastic section modulus of a rectangular cross-section for beam design.
mm
mm
Elastic Section Modulus Sxx
666,667 mm^3
Plastic Section Modulus Zxx1,000,000 mm^3
Shape Factor (Z/S)1.50
Elastic Section Modulus Sxx vs Width (b)
Section Modulus of a Rectangle
Section modulus links bending moment to bending stress directly.
Elastic Section Modulus
S = b h^2 / 6
Derived from S = I / c where I = b h^3 / 12 and c = h / 2.
Plastic Section Modulus
Z = b h^2 / 4
Z represents the full plastic capacity when the entire cross-section has yielded. The ratio Z/S is called the shape factor; for a rectangle it is always 1.5.
Example Calculation
A 100 mm x 200 mm rectangular section.
- 01Sxx = 100 x 200^2 / 6 = 100 x 40000 / 6 = 666,667 mm^3
- 02Zxx = 100 x 200^2 / 4 = 100 x 40000 / 4 = 1,000,000 mm^3
- 03Shape factor = 1,000,000 / 666,667 = 1.5
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