Water content is one of the most important factors influencing rock strength. Considerable research has been carried out to investigate rock strength under both dry and water saturated conditions for different types of sandstones. According to these results, the petrophysical components of rocks (i.e. uniaxial compressive strength, elastic modulus, tensile strength) decrease with increasing water content and this can result in an increase in the mechanical compliance in some cases. In several cases, the strength decrease is remarkable after only 1% water saturation. For rock mechanics and rock engineering projects, it is strongly recommended that the dry uniaxial compressive strength is used for the purposes of strength classification, while for the actual engineering design it is essential to establish the wet strength and ideally the water sensitivity of the rock, in order to asses their potential change in strength and deformability. The goal of this paper is to show a method for calculating the sensitivity of sandstone rocks to water content, using the different published data. From measurements of the density and the uniaxial compressive strength in case of dry and saturated petrophysical states, the strength as a function of water content can be easily determined.