As you may know all Operating Systems has its own calculator software that can help you make simple operations.
If you ever need a more complete calculator with one of these functions.
* scrollable display * up to 50 decimal precisions * unlimited variable storage * intelligent automatic completion * full keyboard-friendly * more than 15 built-in math function * optional keypad
or one of these others
You may need to download and install Speedcrunch.
This calculator is available from repositories for the major Linux Distros.
There is also a Speedcrunch blog where you can read the most recent news about it, and maybe contribute to this project.