The method for calibrating the frequency synthesiser using two-point FSK modulation consists, in a first phase, in supplying an excitation signal generated by a calibration unit to a sigma-delta modulator by deactivating a digital-to-analogue converter and transmitting the output signal from a loop filter of the synthesiser to the calibration unit, which digitally converts the incoming signal and offsets the phase shift between the excitation signal and the loop filter output signal in the calibration unit. In a second phase, the excitation signal is supplied to the sigma-delta modulator and to the activated digital-to-analogue converter, and the digital-to-analogue converter gain is calibrated by checking, in the calibration unit, the polarity of the loop filter output signal with respect to the excitation signal, and using a dichotomy algorithm.