A commercial frequency-modulated (FM) radio signal indoor localization system and method for finding a location of a mobile embedded device (such as a smartphone) within a building. Indoor localization is performed by receiving commercial FM radio signals on the device, analyzing the signals using signal quality metrics, and generating signal quality vectors for each signal and signal quality metric used for the signal. The signal quality metric can be any physical signal quality indicator. The signal quality vectors are added to obtain a current location fingerprint. The current location fingerprint is compared to fingerprints stored in a fingerprint database. The location associated with the stored fingerprint that is the closest match to the current fingerprint location is designated as the current location in the building of the mobile embedded device. Locally generated radio signals can be used in conjunction with the commercial FM radio signals to improve localization accuracy.