RPN Anywhere 4+

Though I am eager to give this app 5 stars, I bought this for use on my Series5 watch but find that there is a bug with WatchOS 7.1 which won't let me swipe to get back to main from the function screens. Unfortunately, the app support page is not in English, so I don't know if there's a workaround.

So why did I give it 4 stars even though it has a debilitating bug? It is unapologetically RPN. The layout and functionality isn't perfect; but it is the most practical design I have seen for writing useful scientific/engineering programs on an iOS device. The layout and functionality on an iPad is stellar.

I will definitely keep this app hoping that the watch bug gets fixed. It is very much worth it's price.

If you're looking for a simple RPN calc that features keyboard input that makes sense (and/of is customizable) compared to the default calculator (in RPN mode) then get this calc.
The only things I wish it had are a few more GUI keys. An EE key in "basic" mode would be nice, and more stack control keys (Roll up/down, Drop) in both modes for when you want to be lazy and only use the mouse. The "scientific" mode already features an EE key and thanks to the programming function I added the stack control keys as programs. Programs appear as keys below the display starting at the left, I added a couple blank programs with spaces for titles to move my stack control keys above the numeric keys. It's almost perfect!

Have been using this app for several years and it is my go to calculator. But one thing is missing. Can you please add a number storage for number recall? Like a memory 1 and Memory 2 button. The stack is great not often I want to perform several different operations on the same number.