Calculator++ - Calculator++ is an advanced, modern and easy to use scientific calculator.
PCalc - PCalc is the powerful choice for scientists, engineers, students, programmers, or indeed anybody...
RealCalc Scientific Calculator - RealCalc Scientific Calculator
Qalculate! - Qalculate! is a multiplatform multi-purpose desktop calculator.
Soulver - Soulver is a software application that functions as a calculator that allows you type a continuous stream of information rather than having to input data into multiple cells.
Gnome calculator - Calculator for the GNOME Desktop Environment, formerly known as gcalc (and gcalctool CLI).