📐 Bending Stress Calculator

Section modulus Wx and bending stress σ = M / Wx — rectangular, circular, hollow and standard profiles

← Back to Engineering

Bending Moment

Design value MEd or characteristic value

Cross-Section

mm
mm
Wx = b · h² / 6

Formulas & notes

Section modulus Wx

Rectangle:    b·h² / 6
Circle:        π·d³ / 32
Hollow rect:  (B·H³−b·h³) / (6·H)
Hollow circ:  π·(D⁴−d⁴) / (32·D)

Bending stress

σ = M / Wx
η = σ / fy ≤ 1.0

Wx is the elastic section modulus Wel,y, so σ = M/Wel is the peak elastic fibre stress. Plastic design uses Wpl,y (≈ 10–15% larger for I-sections) and is a separate ULS check.