Development of instrument for measuring body mass index. By using height and weighing meter gather in the same machine for the convenience in use and body mass index. In order to realize the balance between the weight / height of human. We have a state too fat or too thin. On the end of the series circuit work consists of the amplifier circuit, circuit level signal circuit part to send / receive the load cell function get weight Ultra sonic measuring function and height. By the microcontroller to controlling function of the device weighed and measured height. For use in processing show (body mass index).