The bending stress formula is σ = M × c / I, where σ is the maximum bending stress at point c of the beam, M is the bending moment the beam experiences, c is the maximum distance we can get from the beam's neutral axis to the outermost face of the beam (either on top or the bottom of the beam, whichever is larger), and I is the area moment of inertia of the beam's cross-section. Read more