Abstract Wellbore stability-related problems are one of the main sources of time and money losses in any drilling operation. This is the reason why, in the last years, many improvements have been made in this specific field of research. The improvements are based on a better knowledge of the mechanisms that originate rock failure. One of the key parameters to be controlled and monitored while drilling is that of the mud weight. In order to avoid well instability, a new graphical representation of the safe mud weight window is presented. This new graphical solution is intended to ease the estimation of the values that guarantee well stability, either in tension or compression, at any depth, based on the geomechanical properties of the formations crossed while drilling.