A method and system for calibrating a magnetic compass and/or verifying a compass calibration, using a calibration magnetic field produced by a field-generating coil within the magnetic compass is described. The field-generating coil is located near magnetometers within the magnetic compass. Passing a self-trimming current through the coil produces a magnetic field that acts on the magnetometers. Samples of an output signal from each magnetometer are taken to obtain digital values that indicate the output signal from each magnetometer. The digital values are used by a processor to determine one or more calibration coefficient for using calibrating the magnetic compass. The samples of the output signals are taken when a self-trimming current is passing through the coil and when the self-trimming current is not passing through the coil. Calibration of the compass occurs by applying the one or more calibration coefficients to subsequent signals that indicate the output signals of one or more of the magnetometers.