The invention relates to gyroscopic instruments. The method for calibrating the scale factor of a hydraulic angular velocity sensor or an axisymmetric vibratory gyroscope, which method uses a control amplitude signal, a control precessional signal CP and a control quadrature signal CQ for exciting the vibration of a resonator on a resonant frequency, involves a first step of pre-calibration which consists of measuring and recording an initial scale factor and the value of an initial control signal, and a second step of measuring the value of the current control signal and establishing a scale factor SF that is corrected on the basis of a proportional relationship involving the initial scale factor SF°, the initial value of the control signal Y° and the current value of the control signal Y° according to the formula SF=SF°Y/Y°.