Modem probability fracture mechanics forms the foundation of Carnaby's carpet durability theory. On the basis of this theory, mathematical models have been developed to predict the wear life of wool cut pile carpet. In this paper, the existing models are upgraded to provide an accurate mathematical expression of Carnaby's theory, in line with the current advances in knowledge about the fatigue mechanism of wear in wool carpet, The life distribution function proposed by Camaby is redefined to achieve a direct measurement of the model parameters. The advanced model gives a better fit to the experimental observations than the previous one.