A magnetic field sensor is positioned in proximity to a charging coil in an implantable medical device (IMD). An external device for charging the IMD includes a primary coil and a magnet positioned in proximity to the primary coil. The magnetic field sensor in the IMD detects a static magnetic field of the magnet and provides measurements proportional to the static magnetic field along three axes. These measurements of the static magnetic field are used to determine whether the external device is aligned with the IMD for charging. These measurements of the static magnetic field may also be processed to determine a position of the charger device relative to the IMD in three dimensions. When misaligned, a direction may be generated for a user to reposition the charger device to improve alignment.