Automatic calibration process of the single and double dose of ground and dispensed coffee, of the weighing check and setting of the grinding time type, in order to obtain the desired grammages; said automatic process, for a coffee bean grinder-doser of the electromechanical type and managed by a logic control unit equipped with a management program, and also comprising an electronic weighing device of the load cell type; said automatic process, wherein the desired values in weight for each single or double dose of ground and dispensed coffee are set by the operator in a preliminary phase of start of the apparatus, as a reference, in such a way that the equivalent grinding time (TX, TY) is associated to them (PDX, PDY); said automatic process, characterized in that, during the ordinary coffee dispensings, continuous self-calibration cycles are carried out, in other words identically and autonomously carried out by the grinder-doser, one after the other as a cycle series, wherein these cycles are automatically carried out during the ordinary activity; said self-calibration cycles, are suitable for controlling the actually dispensed quantity of coffee and for modifying from time to time, in every complete cycle, the grinding duration in such a way to get closer to the desired grammages (PDX, PDY) thanks to progressive approximations, in any use condition; said automatic process, for a grinder-doser wherein said weighing device with load cell is integrated (204a-b, 208) in the main body in order to autonomously detect, at the end of each dispensing and with stopped engine, the weight loss corresponding to the actually ground and dispensed quantity of coffee (PX, PY) being said cell directly connected and controlled by the logical unit wherein the necessary instructions for automatically performing said self-calibration cycles are also installed, and namely executed without the intervention of the operator; and wherein each self-calibration cycle includes the following three sequential phases: a) A first automatic checking phase with detection of the actually dispensed dose, wherein at the end of each dispensing, with stopped engine, said load device (204a-b) detects the progressive weight variation insisting on the load cell at least for a number of 3 single doses (PX1-n) and for a number of 3 double doses (PY1-n), in other words carrying out detections one after the other until weighing and recording at least a number of 3 dispensing for each dose (X, Y); b) A second phase for automatically processing the detected data in the previous phase, wherein the new grinding time (NTX, NTY) is determined; c) A third phase for automatically calibrating, wherein in said logic control unit the grinding duration parameters are autonomously re-configured, according to the new grinding time (NTX, NTY) mentioned in the previous phase. a) A first automatic checking phase with detection of the actually dispensed dose, wherein at the end of each dispensing, with stopped engine, said load device (204a-b) detects the progressive weight variation insisting on the load cell at least for a number of 3 single doses (PX1-n) and for a number of 3 double doses (PY1-n), in other words carrying out detections one after the other until weighing and recording at least a number of 3 dispensing for each dose (X, Y); b) A second phase for automatically processing the detected data in the previous phase, wherein the new grinding time (NTX, NTY) is determined; c) A third phase for automatically calibrating, wherein in said logic control unit the grinding duration parameters are autonomously re-configured, according to the new grinding time (NTX, NTY) mentioned in the previous phase.