A new method for the calibration of digitizers is proposed. This method uses the unique ability of the Josephson arbitrary waveform synthesizer to generate almost any waveform with high precision. A complex waveform has been prepared such that the gain of a digitizer, for different frequencies and amplitudes, was calibrated almost simultaneously. The stability of the gain was also evaluated. Other parameters, such as integral nonlinearity, effective number of bits, signal-to-noise and distortion ratio, and others, can be obtained from the same data. The calibration data of a selected digitizer are presented as a demonstration of the concept.