The present disclosure concerns a method for detecting gain or loss of drilling fluid in a drilling installation, said drilling installation comprising a drilling pipe, drilling fluid pits and a hydraulic connection between the pits and the drilling pipe. Said method comprises: providing (116, 118), during a first period, a set of measurement values (vai,m; vcj,m) representative of a volume of drilling fluid in each of the pits belonging to a predetermined group (112, 113); then based on volume measurement values, identifying (148) volume variations occurring during the first period for the pits of the predetermined group, each volume variation of a pit being associated with a volume variation period; calculating (162), for each measuring time (tm), a corrected cumulated volume of drilling fluid (V′m) for the pits of the predetermined group, based on the identified volume variation occurring in at least a sub-group (113) of the predetermined group, and estimating (163) a first value (Am) for a gain or loss of drilling fluid at a measuring time (tm) by comparing the corrected cumulated volume (V′m) with an expected value (V0).