RPN Calc vs GO-21 SciRPN Usage & Stats
A simple reverse polish notation calculator loosely based on my trusty HP-32SII that runs on iPhone, iPad, and Apple Watch!
If you are familiar with HP RPN calculators, the operation of this calculator should seem very straightforward - albeit simplified. It can't be programmed, and it doesn't handle binary, or hexadecimal numbers.
But, it has a clean, simple interface with large, easy to press buttons. It has all of the functions required for quick calculations when your iPhone is handier than your computer or calculator.
And, remember those cool calculator watches from the 1980s? Unfortunately, none of them were RPN. RPN Calc brings a reverse polish notation watch calculator to the Apple Watch!
In addition to the standard RPN Calculator app that runs on iPhone, iPad, and Apple Watch, RPN Calc includes a handy micro RPN Calc Today Extension available for convenient access to quick calculations from the pull down Today screen.
- Apple App Store
- Paid
- Utilities
Store Rank
- -
GO-21 SciRPN simulates the venerable HP-21 Pocket Scientific Calculator from 1975. Virtually indistinguishable from the real item in operation, GO-21 is a powerful yet simple retro calculator.
• RPN (Reverse Polish Notation)
• 10-digit LED calculator display, 10-99 to 10+99
• Four stack registers with roll down
• One storage register with arithmetic memory operators
• Math, trigonometric, polar/rectangular, logarithmic, power and other miscellaneous functions
• One additional window with views of:
◦ stack/storage registers
◦ keystroke log
• Copy-from and Paste-to the calculator display
• Simple Paper Tape annotations
- Apple App Store
- Paid
- Utilities
Store Rank
- -
RPN Calc VS. 
GO-21 SciRPNJanuary 1, 2025