An infant hydration monitor includes a hand-held probe equipped with a pair of arms extending from a housing and incorporating a broadband ultrasonic transmitter and receiver. The arms include finger openings allowing the user to adjust the distance between the transducers by manipulating the probe using fingers placed in these openings. Each transducer is mounted on a force meter so that the skin contact pressure is monitored and optionally communicated to the user using a two-color LED. Sliding distance measuring means similar to the digital caliper are incorporated into the housing to allow the probe to generate a signal indicating the distance between the transducers. A display unit optionally worn on a wrist is attached to the probe and is adapted to calculate the hydration status of an infant.