When a character printed in magnetic ink passes beneath a magnetic reading head it generates a waveform. A method is described here to determine this waveform from the geometry of the printed character. The character shape is divided into elementary vertical units and the height of these units is then tabulated. A single set of experimental data is obtained in the laboratory by passing a magnetically printed bar beneath the same reading head which will be used to read the characters. Formulas are derived in this paper for combining the geometrical data obtained from the character with the experimental data obtained from the laboratory run with the head. A method is then described for programing a high-speed digital computer to derive the waveforms. The discussion explains why these waveforms are often superior to what might be obtained in an actual laboratory run of the printed characters.