Estimation of the water retention capacity of a heterogeneous soil requires knowledge of the hydric properties of each soil phase. Nevertheless, for stony soils, the rock fragments have often been neglected. The objective of this work was then to propose a methodology to improve the calculation of the available water content (AWC) of stony soils at a regional scale. On a 36,200 ha surface area in Beauce located in the Region Centre of France, the AWC was calculated by coupling pedotransfer classes developed for fine earth and rock fragments. When calculating the AWC for the first 120 cm of the soil and considering the rock fragments to be inert, the AWC was underestimated by 15% and showed a high spatial variability. When both the volume and the hydric properties of the rock fragments were ignored, the AWC was underestimated by 20%. This work is then the first proposal to estimate soil water properties at a regional scale by using the water storage capacity of the main part of the stony phase, say from gravels to stones. Results of this study will improve the calculation of water deficit on a regional scale and will aid both in regional water balance modelling and in regional assessment of irrigation needs.