PURPOSE: To decrease thickness and to attain miniaturization by providing a semiconductor pressure sensor in a pocket type portable calculator, connecting the sensor to a calculating function of the calculator and displaying the pressure on a display window.

CONSTITUTION: A pressure added to terminals 4, 4' for measurement of a pressure gauge attached to a surface of the small-sized pocket type calculator 1 is measured by a semiconductor pressure element to display measured numerical values on the display window 3. By putting previously a unit price corresponding to a pressure to this calculator the total amount can be read immediately. Thus, since the titled gauge is used for calculator, it is marketable.