Responsive to a recalibration trigger event, magnetometer data output by a magnetometer can be compared to historical magnetometer data previously output by the magnetometer. If a match is determined, a confidence of the match can be determined using theoretically constant data related to Earth's magnetic field. The constant data can be calculated from the historical magnetometer data. If the confidence of the match exceeds a confidence threshold level, historical calibration data can be used to calibrate the magnetometer. If the confidence of the match does not exceed the confidence threshold level, a calibration procedure can be performed to generate new calibration data, and the new calibration data can be used to calibrate the magnetometer.