A dose measuring device for an inhaler, comprising: an inhalation mouthpiece (3; 73) comprising an outlet conduit for the passage of inhaled air; a powder sensor integrated inside the inhalation mouthpiece (3; 73) and configured for providing a reading of the powder density in the inhaled air inside the outlet conduit of the inhalation mouthpiece (3; 73); a barometric pressure sensor configured for measuring the pressure of the air inside the outlet conduit; a control unit configured for: detecting an inhalation produced in the inhalation mouthpiece (3; 73) by means of analyzing the pressure of the air inside the outlet conduit; the dose measuring device being characterised in that the control unit is configured for: calculating, using the combined information of the powder sensor and the pressure signal of the barometric pressure sensor, a dose of solid particles suspended in the inhaled air going through the outlet conduit in the detected inhalation; wherein for calculating the dose of solid particles going through the outlet conduit in a period of time, the control unit is configured for: - determining, by means of the reading of the powder sensor, the density of solid particles inside the outlet conduit in a plurality of sampling instants (t i) during the period of time; - calculating the airflow going through the outlet conduit in said plurality of sampling instants (t i) using the pressure signal of the barometric pressure sensor; - determining the mass flow rate of solid particles going through the outlet conduit in said plurality of sampling instants (t i); and - integrating the mass flow rate in said period of time. an inhalation mouthpiece (3; 73) comprising an outlet conduit for the passage of inhaled air; a powder sensor integrated inside the inhalation mouthpiece (3; 73) and configured for providing a reading of the powder density in the inhaled air inside the outlet conduit of the inhalation mouthpiece (3; 73); a barometric pressure sensor configured for measuring the pressure of the air inside the outlet conduit; a control unit configured for: detecting an inhalation produced in the inhalation mouthpiece (3; 73) by means of analyzing the pressure of the air inside the outlet conduit; the dose measuring device being characterised in that the control unit is configured for: calculating, using the combined information of the powder sensor and the pressure signal of the barometric pressure sensor, a dose of solid particles suspended in the inhaled air going through the outlet conduit in the detected inhalation; wherein for calculating the dose of solid particles going through the outlet conduit in a period of time, the control unit is configured for: - determining, by means of the reading of the powder sensor, the density of solid particles inside the outlet conduit in a plurality of sampling instants (t i) during the period of time; - calculating the airflow going through the outlet conduit in said plurality of sampling instants (t i) using the pressure signal of the barometric pressure sensor; - determining the mass flow rate of solid particles going through the outlet conduit in said plurality of sampling instants (t i); and - integrating the mass flow rate in said period of time. detecting an inhalation produced in the inhalation mouthpiece (3; 73) by means of analyzing the pressure of the air inside the outlet conduit; the dose measuring device being characterised in that the control unit is configured for: calculating, using the combined information of the powder sensor and the pressure signal of the barometric pressure sensor, a dose of solid particles suspended in the inhaled air going through the outlet conduit in the detected inhalation; wherein for calculating the dose of solid particles going through the outlet conduit in a period of time, the control unit is configured for: - determining, by means of the reading of the powder sensor, the density of solid particles inside the outlet conduit in a plurality of sampling instants (t i) during the period of time; - calculating the airflow going through the outlet conduit in said plurality of sampling instants (t i) using the pressure signal of the barometric pressure sensor; - determining the mass flow rate of solid particles going through the outlet conduit in said plurality of sampling instants (t i); and - integrating the mass flow rate in said period of time. - determining, by means of the reading of the powder sensor, the density of solid particles inside the outlet conduit in a plurality of sampling instants (t i) during the period of time; - calculating the airflow going through the outlet conduit in said plurality of sampling instants (t i) using the pressure signal of the barometric pressure sensor; - determining the mass flow rate of solid particles going through the outlet conduit in said plurality of sampling instants (t i); and - integrating the mass flow rate in said period of time.