The invention relates to a method (200) for determining the sloshing of a liquid loading of a vessel, said method (200) comprising:
a step (206) of determination of a monomodal excitation as a function of a multimodal excitation to which said vessel is subjected, the multimodal excitation comprising a state of the swell and a wind sea state, wherein the state of the swell comprises a direction of the swell and the wind sea state comprises a wind sea direction, and wherein the monomodal excitation exhibits a total direction equivalent to one out of the direction of the swell and the wind sea direction closest to a direction at right angles to the longitudinal axis of the vessel,
a step (208) of determination of a datum relating to the sloshing of said loading as a function of the monomodal excitation.