Kcalc

KCalc has everything you would expect from a scientific calculator, plus:

• Trigonometric functions, logic operations and statistical calculations
• A results stack which enables convenient recall of previous calculation results
• Precision is user-definable
• The display allows cut and paste of numbers
• The display colors and font are configurable, aiding usability
• The use of key-bindings make it easy to use without a pointing device

This tool is part of the KDE Utils Suite.