Abstract: A hand held calculator having a key board with numerical keys and function keys and a visual display is provided at one corner with a rotatable measuring wheel which projects beyond the perimeter of the calculator case so that it can be rolled along a selected line, for example a line on a building plan or map to measure the length of the line. Means is provided for sensing rotation of the wheel and generating a unit signal pulse for each increment of rotation of the wheel. These signal pulses are fed into the calculator circuitry as unit entries and are automatically added to obtain a total measurement entry representing the length of the line. Numerical keys and function keys of the calculator are thereupon manually operable so as to perform additional arithmetic operations on the measurement entry, for example multiplication or division.