Method for the automatic and instantaneous calibration of the dose of ground coffee, or self-calibration, of the type with setting of the desired dose weight in grams, automatic control of the actual weight, automatic recalculation of the duration of grinding and consequent automatic calibration, for a grinder-doser apparatus of coffee in beans of the electromechanical type and managed by a control logic unit with management programs; said grinder-doser apparatus being provided with a weighing device of the electronic type, which is integrated like a base below the main body comprising at least one load cell connected to said logic unit, in such a way as to detect the decrease in weight at every dispensing; and wherein said detection occurs in an independent way, that is to say, separate, from the filter-holding bowl; said grinder-doser apparatus being also provided with a granulometry adjusting means; said method comprising a first setting wherein the operator sets the desired weight in grams of the dose or nominal dose, that is to say, the nominal value in weight of a single dose and of a double dose with which the respective grinding times (TS, TD) are temporarily associated; said method including the automatic control of the decrease in weight after every dispensing and with the motor off, obtaining the exact weight in grams of each dose actually dispensed (DS1-n, DD1-n); said method including the automatic recalculation of the grinding times (TS, TD) carried out as a function of the detected values (103, DS1-n, DD1-n), according to calculation logics included in said management programs of said logic unit; said method including the automatic calibration of the grinder-doser apparatus wherein the grinding duration parameters according to the just recalculated grinding times (TS, TD) are autonomously re-set in the logic unit; said method being characterised in that immediately after said first setting there is a second setting wherein the operator defines the tolerance range and the reliability range (107a, 107b) of the detected values (103, DS1-n, DD1-n), with respect to said nominal values (101, DSN, DDN), and wherein said tolerance range comprises the accepted values, that is to say, the doses considered as compliant and for which no recalculation is provided, whereas said reliability range (107a, 107b) comprises the values of the non-compliant doses and that are considered as realistic and reliable for the purpose of said automatic recalculation (104, TS, TD); said reliability range (107a, 107b) being defined by an upper limit and a lower limit of reliability beyond which there are the anomalous values (109a, 109b), that is to say, unrealistic, which are not considered for the purpose of said automatic recalculation since they are caused by an operating or functional anomaly of the grinder-doser apparatus; said reliability range being divided into a positive reliability range above said tolerance range, and a negative reliability range below it, as an intermediate range between compliant and anomalous values (106, 108a, 108b); said automatic recalculation (104, TD, TS) being automatically carried out according to two alternative operating modes: a first continuous mode that follows an ordinary calculation logic and a second forced mode that follows a forced calculation logic, wherein said calculation logics (LCO, LCF) are included and integrated in said management programs, and wherein said continuous mode is executed during the ordinary practice of use of the grinder-doser apparatus, as a predefined operating mode, which is temporarily interrupted by said forced mode upon occurrence of a granulometry variation, in such a way as to immediately calibrate the grinder-doser apparatus (105, 20) as a function of said variation and thus start again with said continuous mode already updated; and wherein, for the purpose of said automatic recalculation (104, TS, TD), in said continuous mode one only considers the detected values that are out of tolerance and included in said reliability range each time only in positive or only in negative, whereas in said forced mode first the grinding chamber is emptied with non-detected purging dispensings and then at least one sample dispensing is performed whose value in weight is considered in any case for the purpose of said automatic recalculation (104, TS, TD).