Soil depth is an important parameter which is hard to be measured and estimated in hydrogeomorphic and pedological studies. Furthermore, the soil depth is one of the most unknown variables in the hillslope system. Therefore, the objective of the present study was to develop a new equation to estimate the maximum soil depth by using the factor of safety. For this development, a uniform hydrological model was combined to an infinite slope model. The new equation is called MEMPS (Modelo de Estimativa da Máxima Profundidade do Solo). Differently from other equations to calculate maximum soil depth, MEMPS does not require the assumptions of complete saturation or total absence of water in the soil. Thus, MEMPS represents a condition closer to the reality when compared to other equations. Moreover, due to the incorporation of hydrogeomorphic parameters in its formulation, MEMPS acquires fitness to reflect the influence of hydrogeomorphic processes on the soil depth estimation.