Abstract: A measuring apparatus and method for calculating height and weight of human subjects in one step. A scale having a weight sensor is provided to sense the weight of a subject standing thereon. A sonar head is positioned stationary a predetermined distance above the scale sufficient to permit a subject to stand upright on the scale and below the sonar head. The sonar head has a sound wave emitter and a plurality of sound wave receptors. A Digital Signal Processing circuit(DSP) is connected to the sonar head and is activated when the operator initiates a measurement. The data processing circuit is controlled by a software to calculate the weight and height of the subject. The apparatus and method also provides additional data on the subject, such as the body surface area, BA, body mass index BMI, percentiles height and weight. The (DSP) circuit produces a short burst of sound waves that travel downwards, hit the target (patient's head) and return towards the sonar head.