Section Modulus Calculator
Elastic section modulus S and moment capacity M = S·σ for common shapes.
INPUTS
mm
mm
mm
mm
MPa
RESULTS
S — 150×300 rectangle
2,250 ×10³ mm³
Elastic moment capacity M = S·σ
618.75 kN·m
Formula
S = bh²/6
How it works
Section modulus S = I/c condenses a section's bending efficiency into a single number: the moment it can carry per unit of stress, M = S·σ. Steel tables list S directly so engineers can pick a section in seconds — find the required S = M/σallow, then choose the lightest shape that provides it.
Worked example
A 150×300 mm rectangle: S = bh²/6 = 150·300²/6 = 2250×10³ mm³. With S275 steel that's an elastic moment capacity of M = 2250e3·275/1e6 = 618.75 kN·m... for timber at 10 MPa it's 22.5 kN·m — same shape, 27× less.
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