If you have fat fingers and the size of the buttons on the official calculator app are not large enough for you to type in a hurry, here is an app for you: Nirmit Kavaiya’s Gestulator. The app ekes out more space for the numerals by completely getting rid of all numerical operators – so how do you enter plus? Well, just swipe up anywhere on the app. Swiping in any of the cardinal directions will reveal the numerical operator. Release your finger to enter it.
The marketplace description is concise:
Gestulator is a simple and clean Gesture based Calculator.
Use the number pad to enter values, Swipes for arithmetic operations, and other Gestures to clear, remove values
Gestulator is free on the marketplace.