The water spray systems is widely used for fire safety area and is a well-established technique for providing safety and protection of nuclear installations and also in industrial facilities. One major challenge is to be able to properly determine the technical features of the water spray system that are required for predictive simulations. For that, a Phase Doppler Interferometer (PDI) device, that is a complex and challenging laser technique, is often used to measure the droplet size distributions and the droplet velocities. However, some usual water spray models can require as input parameters only an overall droplet size distribution and an initial velocity and some statistical methods are needed to determine them from local accurate measurements. In this paper, it is addressed a new calibration approach for assessing the input parameters of this modeling by using large-scale and wellcontrolled fire tests. Then, by introducing some correlations to take into account different operating conditions of the pressure at the nozzle head, this technique is validated on other large-scale fire tests. After discussing thoroughly the results, this new method shows that it can be a valuable and efficient tool for determining the overall features of water spray systems linked with the modeling of water spray system used in this study.