My second Windows 8 App has just been released by Microsoft. The XXL Calculator is a calculator App with extra large Buttons and display. You can download it from the Microsoft App Store.

Some screenshots

XXL Calculator: Extra large buttons and display

It is especially handy in snapped mode, aside another App:

In snapped view, aside an Excel sheet

Compact mode is also supported:

Compact mode: Size automatically adjusted

Of course, the full-screen portrait mode is also possible:

In portrait mode, full-screen

Also, there is a special dark theme for all modes, ideal for high contrast or night usage:

Dark theme: Works in all view modes, One-click toggle.