Calculated Industries 6020 Scale Master Classic Rolling Calculator w/ Dimensional Math and U.S. to Metric Conversions BUILT-IN DIMENSIONAL UNITS: Work in decimal inches, feet-inches, decimal feet, yards, miles, nautical miles, millimeters, meters, kilometers -- all in square and cubic formats CUSTOM SCALES: Six preset slots available -- 3 in U.S. and 3 in Metric -- for you to define your own scales AUTOMATIC RECTANGULAR VOLUMES: Roll this tool over the length and width of a rectangle, and it will automatically calculate the square footage on your plan ACCUMULATING MEMORY: Use the M+ function to total dimensions or counts for multiple-page plans POWER SAVING: Auto shutoff feature saves power and time