There are a few calculators available for Linux, I'll show you a few of theme.

gcalctool

It's a simply calculator pre-installed with sidux.

1. Run it from: Menu-> Accessories-> Calculator.

2. If the application has been not installed do it yourself:

apt-get install gcalctool

Home page: http://calctool.sourceforge.net/

Extcalc

Extcalc is a multi-functions scientfic calculator lets you for example drawing 2D- and 3D-graphs and

function-analysing for all supported graph types. Text-based version to use on a console too.

1. Installation:

apt-get install extcalc

2. Run it from: Menu-> Accessories-> Extcalc

3. The application ask you for making it's own folder for dates so click OK.

Home page: http://extcalc-linux.sourceforge.net/

Xabacus

Xabacus is not a typical calculator, it's a kind of ancient abacus but you can work on it anyway.

It's Chinese name is "Saun-pan" or "Suanpan".

1. Installation:

apt-get install xabacus

2. Run it: Menu-> Accessories-> Xabacus

About Suanpan on Wikipedia: http://en.wikipedia.org/wiki/Suanpan

About Abacus on: http://en.wikipedia.org/wiki/Suanpan

Others

1. Speed Crunch: http://speedcrunch.org/en_US/index.html
2. Qalculate: http://qalculate.sourceforge.net/
3. Eden Math: http://www.edenwaith.com/products/edenmath/
4. Kcalc: http://packages.debian.org/pl/sid/kcalc