Qalculate! (GTK UI)

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).

Features include a large library of customizable functions, unit

calculations and conversion, physical constants, symbolic calculations

(including integrals and equations), arbitrary precision, uncertainty

propagation, interval arithmetic, plotting, and a user-friendly interface.