Most users are usually more comfortable with the default calculator interface for calculations. However, if you require advanced calculation features along with the default interface then take a look at the free Calculator app by CyanogenMod developers.
The app has a Halo theme based interface that CyanogenMod is known for along with the option to choose a dark or a light theme. The first page gives you the most basic calculator with a large numeric keypad. However a simple swipe to the left or right brings up advanced features of the app.
Swipe right to switch between calculation bases. You can choose to work with the decimal base (default), binary or hexadecimal as per your requirement. Another right swipe brings up the Graph page where you can input value for X and Y to create an instant graph.
Swipe left to access functions like Trigonometry (sin, cos, tan) and inverse trigonometry along with various other advanced calculation symbols. Continue to swipe left to access the matrix menu for calculations.
You can choose to keep or remove any of these panels from the app settings. The app also lets you view a usage history of from the basic panel in case you want to recheck anything.
As usual with CyanogenMod developers, the app is free from any advertisements.