The built-in Calculator app is a most used Windows 8 application with basic function and useful for somebody who need to calculation on the Surface tablet.
How to Open Windows 8 Calculator With Shortcut on Surface
* Swipe your finger from left corner to right, and choose “Search” in Charms Bar.
* Type “Calculator” in the box and tap “Apps” from the bottom. The app will appear in the result.
* Tap and hold on Calculator, and tap on “Pin to Start” in the bottom options bar. Now you can run Calculator from Start screen.