Systems and methods for determining whether a mobile device is indoors or outdoors based on ambient signal measurements are described herein. A method for performing indoor/outdoor detection for a mobile device as described herein includes identifying one or more selected radio channels, including at least one of amplitude modulation (AM) radio stations, frequency modulation (FM) radio stations, or television stations, in an area of the mobile device; obtaining information relating to reference outdoor signal strengths for the respective selected radio channels; calculating measured signal strengths for signals received via the selected radio channels; comparing the reference outdoor signal strengths and the measured signal strengths; and classifying the mobile device as indoors or outdoors based on a result of the comparison.