Abstract <p>The inherent imperfections within the metal bellows hold substantial sway over their failure modes and fatigue life, necessitating a meticulous examination. The intricacies of fatigue life assessment of bellows are explored, incorporating three pivotal factors like the positioning, length, and penetration depth of preexisting cracks. Furthermore, the stress amplification factors for bellows afflicted with preexisting cracks are carefully analyzed. A revised fatigue life calculation formula is presented, which adeptly accounts for the presence of preexisting cracks. The implications of three distinct defect types on the fatigue life are rigorously studied, revealing that such initial imperfections can significantly curtail the minimum expected life span of bellows.</p> Graphical abstract <p></p>