Low complexity performance characterizations of error-correcting codes are needed to better exploit their potential when adapting a communication system to channel conditions or to service requirements. For the case of turbo-codes, existing performance characterizations are often too complex or not flexible enough to be used for real-time adaptation. This paper presents a new technique for evaluating the performance of turbo-codes, that may fit the need for flexibility and low-complexity. It enables the determination of the error-free decoding threshold and of the number of iterations to achieve error-free decoding. Its complexity is far lower than that of existing methods and its accuracy is very satisfying.Anglai