An instrumented comb, including bristles protruding from the handle, the bristles spaced apart from each other such that a first set of two or more bristles are spaced by a first distance, a second set of two or more bristles are spaced by a second distance, and a third set of two or more bristles are spaced by a third distance, wherein the third distance is greater than the second distance and the second distance is greater than the first distance. The comb includes a controller receiving signals from: a contact sensor to detect contact with a scalp, and a magnetic compass to determine location on the scalp. The comb uses the signals to record the detected contact information and determined location information as the comb undergoes a brushing gesture over a scalp, measure hair density based on the contact information and location information, and output the measured hair density.