PG Calculator works in RPN mode. It recognizes real and complex numbers and allows vector manipulations. There are up to 120 recognized units of measure with possibility to make ease conversions between consistent units.
PG Calculator enables number inputting in binary, octal, hexadecimal, and exponential formats. It has up to 80 built-in functions: algebraic, trigonometry, hyperbolic, logical, numbers format convertions, units of measure conversions and statistical.
It is available for free download at http://www.pgcalc.net/pgcalc2-2.1.tar.gz.