Coffee grinder with weight control device of the dose of ground coffee, of the type comprising an electric motor, a grinder group driven by said electric motor and housed inside a grinding chamber, a feed hopper for feeding the coffee beans to be ground towards said grinding chamber, a support fork for supporting a filter holder to be leaded with ground coffee, a delivery channel for delivering the ground coffee towards said fork, a load cell mechanically connected to said fork and a microprocessor which controls the operation of the motor to determine a desired final dose (Pf) of ground coffee inside said filter-holder, characterized in that said microprocessor contains control firmware which, when weighing a new dose of coffee is required by the user, activates a weighing program which provides the following operational steps in succession: a) activating the electric motor to obtain the coffee grinding by the grinder group; b) continuously controlling, by said load cell, the detected weight (Pr) of ground coffee which, through said delivery channel, reaches the filter-holder leaning on said fork; c) determining the shutdown of the electric motor when said detected weight (Pr) reaches the value Pr=Pf-Δ where Δ is a predetermined value corresponding to the weight of ground coffee which reaches the filter-holder during the shutdown transient of the electric motor, wherein said Δ value is initially predetermined experimentally, depending on the constant characteristics of each individual type of coffee grinder, and is thus continuously calibrated during the operation of the coffee grinder, depending on the variable conditions in which said coffee grinder is operating, characterised in that the control firmware of said microprocessor further provides a continuous calibration program of said Δ value which comprises the following operational steps: d) storing a predetermined number (n) of subsequent weighings; e) calculating the mean weigh value on said number (n) of subsequent weighings; f) determining the mean deviation between said mean weigh value and the final value (Pf) of the desired weighing; g) modifying the Δ value directly proportional to said mean deviation, wherein in said step d) the weigh values are acquired, passing to the following step e), only when all the weighings have the same variation sign with respect to the final value (Pf). a) activating the electric motor to obtain the coffee grinding by the grinder group; b) continuously controlling, by said load cell, the detected weight (Pr) of ground coffee which, through said delivery channel, reaches the filter-holder leaning on said fork; c) determining the shutdown of the electric motor when said detected weight (Pr) reaches the value Pr=Pf-Δ where Δ is a predetermined value corresponding to the weight of ground coffee which reaches the filter-holder during the shutdown transient of the electric motor, wherein said Δ value is initially predetermined experimentally, depending on the constant characteristics of each individual type of coffee grinder, and is thus continuously calibrated during the operation of the coffee grinder, depending on the variable conditions in which said coffee grinder is operating, characterised in that the control firmware of said microprocessor further provides a continuous calibration program of said Δ value which comprises the following operational steps: d) storing a predetermined number (n) of subsequent weighings; e) calculating the mean weigh value on said number (n) of subsequent weighings; f) determining the mean deviation between said mean weigh value and the final value (Pf) of the desired weighing; g) modifying the Δ value directly proportional to said mean deviation, d) storing a predetermined number (n) of subsequent weighings; e) calculating the mean weigh value on said number (n) of subsequent weighings; f) determining the mean deviation between said mean weigh value and the final value (Pf) of the desired weighing; g) modifying the Δ value directly proportional to said mean deviation, wherein in said step d) the weigh values are acquired, passing to the following step e), only when all the weighings have the same variation sign with respect to the final value (Pf).