Abstract: The crack leakage is a key parameter to determine whether the candidate pipe meets the requirements of leak before break application. Study on the theory of crack leakage calculation was performed, and a computer code named PICLES was developed. For more convenience usage, the ability of calculating leak crack length directly was also implemented. The software is verified by comparing the calculation with the target software. The results show that PICLES has the same result with the target software for same inputs and is more efficient. PICLES can be used for the evaluation of leak before break of pipes..