# RPN Calc > Simple reverse Polish notation calculator for iOS devices and Apple Watch. (iPhone/iPad app by James Mattis.) - Source: https://appshunter.io/ios/app/rpn-calc/id285002799 (this page in markdown: same URL + `.md`) - Developer: [James Mattis](https://appshunter.io/developer/285002802) - Category: Utilities, Productivity - Price: $0.99 - Rating: 4.40/5 from 5 App Store ratings · 25 written reviews indexed - Age rating: 4+ - Requires: iOS 16.0 · 3 MB - Languages: American English - Released: 2019-01-31 - Data updated: 2026-08-18 - Monetization: free - User reviews in markdown: https://appshunter.io/ios/app/rpn-calc/id285002799/reviews.md ## What is RPN Calc? 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. ## Key features - Reverse Polish Notation (RPN) input - Clean, simple interface - Large, easy-to-press buttons - iPhone, iPad, and Apple Watch support - Today Extension for quick access ## Chart rankings - #196 in Top Paid · Utilities (US App Store) ## Recent user reviews (10 of 25) All indexed reviews: https://appshunter.io/ios/app/rpn-calc/id285002799/reviews.md ### 5/5 — Awesome App *2025-10-02* Had unbelievably awesome support from the developer. The app is packed with features that are so convenient to have right on my wrist, not to mention iPhone and iPad. Thanks for this app and true support. ### 1/5 — Watch complication *2025-09-26* Latest watch complication broken. Will not run ### 4/5 — Definitely worth considering. *2025-05-29* I bought this app hoping to replace the rpn app Pcalc on my iPad dock - and it has done that successfully. The reason is that on my iPad I’m very often trying to use the calculator in a slide over or side by side with another app. This app does not hog the entire iPad screen when it’s the only app that’s open. So, with the iPad in landscape mode it does a really great job with split screen or slide over. Calculator widgets have functionality problems and this app doesn’t have a widget - no problem. The appearance is also very neat and clean, a very good looking design. I’ve had a bunch of different HP rpn calculators since the 1970’s, and now have no interest in apps that recreate those designs. The advanced functions of this app are quite good, sufficient for my needs and the conversion factor mode is really far beyond my need for a retired guy. There is only one major shortcoming - memory storage. I use that quite often with pCalc and any other calculator. I think that most people who are rpn addicts likely have that same need. Without memory storage it’s a bit troublesome. With it it would be a a five star app for its practicality. ### 4/5 — Clean Design... But need one one thing *2017-11-05* Nice layout. Works well but needs one more thing. It is very necessary to have an x(exchange)y function on the keyboard. Many calculations need this capability to set up for a solution as RPN uses the x-y order for them.... Please add this to an update if you can. ### 4/5 — Close to perfect *2016-01-13* I love this for my watch it it could really use square root key ### 4/5 — Works well on Watch and Widget *2015-08-02* I have always liked RPN calculators more than algebraic. This is a fairly simple RPN calculator that works surprisingly well as a widget but also on the Apple Watch. It has a four level stack. It does have an unusual behavior where if the stack is full and you add up all the numbers the number that was on the top of the stack is repeated ad infinitum in the Y position. If you pay attention to what you're doing this should not cause a problem but I found it odd. I would like to see instructions included as well as sound effects in the widget so that when I press on the key there is a click or tone. ### 2/5 — Has problems *2014-11-15* Not full screen. Keys are small. Background around calculator bright white making it hard to see. Background should be black or calculator should be full screen. ### 4/5 — Good Basic RPN Calculator *2011-07-27* Simple RPN calculator that keeps me from having to reach for my 30 year old HP-11C most of the time. The ability to do unit conversions is worth the price by itself. ### 4/5 — Excellent RPN calculator *2010-09-10* Just as advertised - very clean, simple rpn calculator. It works perfectly, beautifully designed, no crashes. It has all the functions you are likely to need for scientific calculating. The unit conversion feature (actually, quite extensive) is a very nice extra. Suggestions for updates/improvements: have the calc float over the background wallpaper rather than having a completely white background, and ability to position to calc over the background and remember its position. This would be nice when iPad allows multitasking. A row of storage registers might be nice. Maybe showing more registers than the x and y registers is something to consider, but would probaby ruin the beautiful simplicity this calculator displays. ### 3/5 — Getting Better *2008-12-16* The stack looks like it has been fixed. I found that the tangent of pi yields a -0.00. This could be fixed but overall much better then when I initially downloaded the program. It has become my preferred calculator app. ## Frequently asked questions about RPN Calc ### What is RPN Calc? RPN Calc is a mobile application that functions as a reverse Polish notation (RPN) calculator. It is designed to offer a simplified RPN experience inspired by classic HP calculators, available on iPhone, iPad, and Apple Watch. ### What are the key features of RPN Calc? Key features include its RPN input method, a clean and simple interface with large buttons for ease of use, and compatibility across iPhone, iPad, and Apple Watch. It also includes a Today Extension for quick access from the pull-down screen. ### How much does RPN Calc cost? RPN Calc is available for free. The provided information indicates no in-app purchases or advertisements, suggesting a completely free experience for users. ### What devices is RPN Calc compatible with? RPN Calc is compatible with Apple devices, specifically running on iPhone, iPad, and Apple Watch. It also offers a Today Extension that can be accessed from the pull-down Today screen on compatible iOS devices. ### Who would benefit from using RPN Calc? Users who are familiar with and prefer the reverse Polish notation (RPN) method of calculation will benefit from RPN Calc. It's ideal for those who need a quick and straightforward calculator on their iPhone, iPad, or Apple Watch, especially if they appreciate the functionality of older HP RPN calculators. ## Version history (last 5 releases) ### 13.1.0 — 2026-08-13 - An updated Watch interface with a new math function screen accessed by up / down swipes or by using the Digital Crown. ### 13.0.7 — 2025-10-01 Updated for iOS 26, iPadOS 26, watchOS 26, and visionOS 26! ### 13.0.6 — 2025-09-23 Updated for iOS 26, iPadOS 26, watchOS 26, and visionOS 26! ### 13.0.5 — 2024-12-18 - Updated for iOS 18, iPadOS 18, WatchOS 11, and VisionOS 2! - Interface refreshed and updated with a clean, modern design! ### 13.0.4 — 2024-09-20 - Updated for iOS 18, iPadOS 18, WatchOS 11, and VisionOS 2! - Interface refreshed and updated with a clean, modern design! ## Apps similar to RPN Calc | App | Rating | Price | Category | | --- | --- | --- | --- | | [My RPN Calculator](https://appshunter.io/ios/app/my-rpn-calculator/id1451441996) | — | $4.99 | Utilities | | [RePNCalc - RPN Calculator Pro](https://appshunter.io/ios/app/repncalc-rpn-calculator-pro/id969780852) | 5.0 (1) | Free | Utilities | | [3D Stress](https://appshunter.io/ios/app/3d-stress/id6503481793) | — | $2.99 | Utilities | | [GO-21 SciRPN](https://appshunter.io/ios/app/go-21-scirpn/id327651563) | 4.9 (13) | $2.99 | Utilities | | [My RPN Calc](https://appshunter.io/ios/app/my-rpn-calc/id807032892) | 3.0 (2) | $1.99 | Utilities | | [RPN-Calc](https://appshunter.io/ios/app/rpn-calc/id6464329997) | — | $4.99 | Utilities | ## More apps by James Mattis - [Drug Search](https://appshunter.io/ios/app/drug-search/id326294946) All apps by James Mattis: https://appshunter.io/developer/285002802 ## Related topics [touch rpn calc](https://appshunter.io/ios/topics/touch-rpn-calc) · [rpn calc pro](https://appshunter.io/ios/topics/rpn-calc-pro) --- *Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-08-18.*