Abstract This study is motivated by the lack of information regarding seismic analysis and design of liquid-filled conical tanks. The main challenge in this type of fluid–structure interaction problem is the estimation of the forces associated with the hydrodynamic pressure resulting from the vibration of the structure. A simplified mechanical analog that can be used to estimate the forces associated with horizontal ground excitation is developed in this study. The proposed mechanical analog takes into account the flexibility of the tank walls and simulates both the impulsive and sloshing components of the hydrodynamic pressure. Parameters of this analog are displayed in chart form as functions of the geometrical parameters of the tanks including the angle of inclination of the tanks’ walls. Finally, an example is provided to illustrate the application of the developed analog for evaluation of the response of liquid-filled conical tanks to horizontal ground excitation.