Well casings are designed against burst strength pressure. The same formula is used in determining the remaining burst strength pressure of casing that suffered from wear. API 5C3 and ISO 10400 burst strength models are widely used to determine the burst strength pressure and the remaining strength of casing. This paper focus on the comparison of both burst strength models for its reliability assessment for vertical well casing. The limit state design method was used and adapted into this study to calculate the probability of failure for both burst strength models. The reliability analysis for both models is conducted using Monte Carlo simulation. The results show that ISO 10400 burst strength model can predict the probability of failure for vertical well casing when subjected to higher operating pressure compared to API 5C3 burst strength model. ISO 10400 burst strength model can predict probability of failure for higher operating pressure due to adaption of ultimate tensile strength as the strength parameter in the equation whereas API 5C3 has adopt yield strength as the strength parameter in the equation. © The Authors, published by EDP Sciences, 2018.