A method for determining an estimated mass of an aircraft is provided. This method includes determining a first mass of the aircraft, from characteristics of the aircraft determined before or after takeoff of the aircraft, determining, during the flight of the aircraft, a second mass of the aircraft, from a lift equation of the aircraft expressing the mass of the aircraft as a function of information representative of the load factor of the aircraft, of a lift coefficient of the aircraft, of speed information of the aircraft and of a static pressure of a mass of air passed through by the aircraft, determined from measurements by sensors of the aircraft during the flight of the aircraft, evaluating the estimated mass at said determination moment, as a function of said first and second masses.