Abstract: A dedicated calculator for performing arithmetic operations on dimensioned quantities, particularly those in the English units of feet, inches and fractions of inches. The calculator keyboard includes a plurality of conventional algebraic calculator keys as well as dedicated keys for entry of values in inches and fractions of inches. A display provides formatting according to the mode of operation and the result. The calculator operates in modes for displaying feet, inches, and fractions of inches; decimal feet; metric values; and to operate as a conventional algebraic calculator. All numbers are stored internally as binary floating point numbers representative of values of feet. Therefore, all values are preserved when switching from metric mode to one of the foot modes and any conversions of the output to metric measurements are only made to the data to be displayed.