iStatCalc is a simple and easy-to-use calculator!
You can simply add a number in a list by pressing "=" button, and / or a number is listed as calculation result. Simultaneously, it displays "summation", "average", "maximum", "minimum", and "count" of these numbers in the list.
Because a number is listed as entered or calculated, you can keep track of what has been added and you can even go back and access to each number for modification or deletion.
There are also three different type of themes available - Monotone, Green, and Orange. You can choose the theme you wish to see depending on the mood that you are in.