Abstract: The apparatus of this invention relates to an optical counting apparatus which is to be employed in combination with an electronic handheld calculator. The structure of this invention greatly expands the use of the handheld calculator by permitting such to be employed as a measuring device and a unit counter. An optical device is activated by the difference between transmission of light and darkness. This activation is used as a counting apparatus or a measurer of distances with the accumulated count or the distance measure to be read on the dislay unit of the calculator.