SpeedCrunch is a free, fast, high precision open source algebraic calculator with an intuitive interface and many features, such as variables, syntax highlighting, functions, persistent input history & more.
Qalculate! is a multi-purpose cross-platform desktop calculator. It is simple to use but provides power and versatility normally reserved for complicated math packages, as well as useful tools for everyday needs (such as currency conversion and percent calculation).
Kalk is a convergent calculator application built with the Kirigami framework. Although it is mainly targeted for mobile Linux platforms, it can also be used on the desktop.
PCalc is the powerful choice for scientists, engineers, students, programmers, or indeed anybody looking for a feature rich calculator. It includes an optional RPN mode and multi-line display, a choice of button layouts, an extensive set of unit conversions and constants, a...