A method and device for calibration of a three-axis magnetometer that facilitates a more efficient and routine procedure by calibration of hard and soft iron errors of a 3D-magnetometer integrated into a mobile electronic device, and a set of operations for coprocessing measurements of the 3D-magnetometer and inertial sensors (e.g., a 3D-accelerometer and 3D-gyro), which can determine magnetic heading and attitude of the electronic device.