Calculation of the decision threshold and detection limit of a measurement, or measurement method, are crucial in order to decide if an analyte is present or not and with what confidence it can be quantified. That decision is important in view of possible actions if something would be detected. In this work, a method for calculating these limits using a Monte Carlo method is presented. In the Monte Carlo method any a priori distribution (e.g. normal distribution, rectangular distribution, triangular distribution) of an input quantity can be selected. Differences between the Monte Carlo calculated characteristic limits and the ones calculated according to ISO 11929:2010 is presented. Moreover, suggestions how to calculate the detection limit when it can not be calculated according to the ISO 11929:2010 are given.