RPN Calc vs RPNPro
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
RPN Calc
This app provides a straightforward reverse Polish notation (RPN) calculator experience, inspired by classic HP models. It offers a clean interface with large buttons for quick calculations on iPhone, iPad, and Apple Watch, along with a convenient Today Extension for immediate access.
- Reverse Polish Notation (RPN) input
- Clean, simple interface
- Large, easy-to-press buttons
- iPhone, iPad, and Apple Watch support
- Today Extension for quick access
Read full descriptionHide full description
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.
RPNPro
This calculator utilizes Reverse Polish Notation (RPN) for input, mirroring the functionality of classic HP calculators. It features a four-level stack with X, Y, Z, and T registers, displaying the X register in decimal, hexadecimal, and binary.
- Reverse Polish Notation (RPN) input
- Four-level stack (X, Y, Z, T registers)
- Decimal, hexadecimal, and binary display
- Modeled after HP calculators
- Designed for software engineers
Read full descriptionHide full description
RPNPro is a calculator for software engineers. RPNPro uses RPN (Reverse Polish Notation) as an input scheme. It is based on the same four level stack model as provided by the original HP (Hewlett-Packard) calculators, featuring X, Y, Z and T registers. The contents of the X register are always shown in decimal, hexadecimal and binary notation.
Screenshots
Verdict
The clearest difference is price: RPNPro at Free against RPN Calc's $0.99. RPNPro also leads on rating (5.0 vs 4.0) and review sentiment (50% vs 38%). RPN Calc's advantage is update cadence (every 3 months vs every 37 months) and ratings volume (6 vs 1). On ads, in-app purchases, monetization model and device support there is nothing between them.
Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS
RPNPro is free to download; RPN Calc costs $0.99 up front. Neither carries in-app purchases, so what you see is what you pay.
RPNPro holds the better App Store score, 5.0 against 4.0. That said, the two scores are not equally well evidenced: RPN Calc has 6 ratings behind it against 1, so its average is the more settled of the two. Written reviews point the same way: 38% of RPN Calc's written reviews are positive against 50% of RPNPro's.
RPN Calc ships an update every 3 months, RPNPro every 37 months. The most recent releases landed on October 24, 2026 and October 14, 2026 respectively.
| Parameter | RPN Calc | RPNPro |
|---|---|---|
| Price | $0.99 | Free — better |
| Rating | 4.0 (6 ratings) | 5.0 (1 ratings) — better |
| Positive reviews | 37.9% of reviews | 50.0% of reviews — better |
| Number of ratings | 6 — better | 1 |
| Update frequency | Every 3 months — better | Every 37 months |
| Ads | No | No |
| In-app purchases | No | No |
| Monetization | Free | Free |
| Devices | iPhone, iPad, Apple Watch | iPhone, iPad, iPod |
| Requires iOS | 16.0 | 9.1 — better |
| Further details — not scored | ||
| Size | 3 MB | 1 MB |
| Age rating | +4 | 4+ |
| Developer | James Mattis | Felix Meier |
Customer experience
RPN Calc
RPNPro
In-app purchases
RPN Calc
No in-app purchases
RPNPro
No in-app purchases
