A correlation is demonstrated to predict the reduction in the mean length-to-diameter ratio of catalyst extrudates by breakage due to stress in a fixed bed. The stress can be caused either by the reactor load or it can be externally applied as in the bulk crush strength measurement. The strength characteristic of particular interest here is the extrudate bending strength characterized by the Euler-Bernoulli modulus of rupture. The balance of the bending strength to the applied stress leads to a new dimensionless group. Extrudates in a fixed bed start to break above a specific critical stress, and their mean length-to-diameter ratio then becomes linearly proportional to this dimensionless group to the power one-third.