This is a simple RPN Calculator which can use on iPhone and Apple Watch. Watch App has same functions with iPhone App. How to use - To push the value you typed, tap green up-arrow button placed on bottom-right - To delete last typed digit, swipe right on anywhere in screen - On Apple Watch, all values in stack is shown when you swipe down on the screen - On Apple Watch, the number of values in stack is shown at top-left of the screen