Abstract: A portable body fat monitor is provided having electrodes arranged so that the instrument is easily operated by a user, thereby facilitating accurate measurements. Embodiments include a portable body fat monitor having an insulating main body, shaped substantially like a rectangular parallelepiped. Four electrodes are spaced apart from one another on a side surface of the main body. A display unit, such as a liquid crystal display, is disposed on a front face of the main body, and an operator unit, such as a set of push buttons, is located below the display unit on the front face of the main body. To operate the monitor, a user enters numerical values representing his or her height and weight with the thumbs of their right and left hands. The middle and index fingers of the user's left hand are then brought into contact with two of the electrodes, respectively.