In the determination of the laser-induced damage threshold of optics, the correct estimation of damage probabilities is essential. In this publication, a simple procedure based on physical considerations is proposed to optimize the calculation of the damage probabilities by using a cumulative algorithm. The predicted status of test sites at higher and lower fluences than actually tested provides the basis for a new data reduction. It is shown that the proposed algorithm increases the statistically relevant amount of data per fluence interval dQi by using virtual test sites. Thus, the uncertainty σi in the calculation of the damage probabilities is reduced significantly and the subsequent linear regression of the damage probabilities will have a reduced least squared error. Non-linear regression of the damage probability according to defect-induced damage models as published numerous times in recent years are also performed to utilize a better confidence level which will be shown exemplarily.