W = Force (N)
L = Length (mm)
M = Bending
y = Distance from Neutral axis to fiber - usually extremity (mm)
E = Young's Modulus or Mod of Elasticity (convert to MPa)
I = 2nd Moment of Area or Area Moment (mm4)
Z = Section Modulus (mm3) = I / y
Bending Stress = M*y / I = M / Z (MPa) which is maximum tension (or compression) at bottom (or top) of beam.
If column is "slender" it is likely to buckle when in compression.