fxCalc

fxCalc is a scientific calculator with an intuitive, keyboard-driven interface

fxCalc is a scientific calculator featuring a keyboard-driven, worksheet based interface, and strict left-to-right operator precedence. fxCalc is very intuitive and simple-to-use, with scrollable history supporting commenting and annotation. But it's also very powerful, with support for user-defined variables, lots of built-in mathematical functions, special functions to evaluate series, support for comparison operators and logical operators, and much more. It also comes with an in-app reference manual.