# RPN Calculator 48 — RPN Scientific Calculator

> RPN scientific calculator with undo/redo and HP 48-inspired design. (iPhone/iPad app by Tom Kerrigan.)

- Source: https://appshunter.io/ios/app/rpn-calculator-48/id336580727 (this page in markdown: same URL + `.md`)
- Developer: [Tom Kerrigan](https://appshunter.io/developer/295445504)
- Category: Utilities, Productivity
- Price: $3.99
- Rating: 4.80/5 from 238 App Store ratings · 144 written reviews indexed
- Age rating: 4+
- Requires: iOS 18.0 · 1 MB
- Languages: American English
- Released: 2009-10-30
- Data updated: 2026-08-26
- Monetization: paid
- User reviews in markdown: https://appshunter.io/ios/app/rpn-calculator-48/id336580727/reviews.md

## What is RPN Calculator 48?

RPN Calculator 48 is a polished RPN replacement for Apple's calculator app:

- Same scientific functionality as Apple's calculator app*
- Use swipe gestures to undo and redo operations!
- Starts quickly
- Large buttons
- Easy-to-read display
- 100 entry stack
- 6 memory buttons (A-F)
- 50+ levels of undo/redo
- Saves state on exit

The ergonomics (screen and keyboard layout) of RPN Calculator 48 were inspired by HP's outstanding 48-series calculator.

RPN Calculator 48 is made by the developer of tChess (the critically acclaimed iPhone chess game) and Learn Chess (the Apple Staff Favorite e-book).

* This app is not an HP 48 emulator.

## Key features

- Reverse Polish Notation (RPN)
- Scientific calculator functions
- Swipe gestures for undo/redo
- 100 entry stack
- 6 memory buttons
- State saving on exit

## What do users think of RPN Calculator 48?

Overall sentiment: positive

**Pros**

- 🚀 Excellent RPN implementation
- 👍 Familiar and intuitive interface
- 💡 Useful features for everyday calculations
- 🚀 Reliable and stable performance
- 👍 Large and visible stack display

**Cons**

- 🐛 Lack of landscape mode support on iPad
- 💡 Could use more advanced features like matrix operations

**Commonly reported bugs**

- Display issues in landscape mode on iPad

**Most requested features**

- Add haptic feedback for key presses
- Implement ability to recall previous calculations from stack
- Improve landscape mode support on iPad

## Recent user reviews (10 of 144)

All indexed reviews: https://appshunter.io/ios/app/rpn-calculator-48/id336580727/reviews.md

### 5/5 — RPN Heaven

*2026-08-10, version 1.0.8*

I retired my HP35 when I got this app. It’s so much more efficient doing complex calculations. Love it!

### 5/5 — Very useful

*2026-07-16*

It's convenient to have most of the everyday functions of the hp48 with some added features (like more visible stack, bigger keys, undo, ....).

My favorite RPN app.

### 5/5 — Very Good hp 48/49 Emulator

*2026-04-16, version 1.0.8*

All self respecting engineering school students used the hp (real hp before Compaq merger) 48 and swan song 49 handheld calculators. I am amazed how tell this emulates it. With today’s dollars the real calculators sold for roughy $4k.

### 5/5 — Goldilocks RPN

*2026-03-21, version 1.0.8*

This calculator is just the right mix of features/functions from the wonderful 48 series machine. For those fortunate enough to have learned RPN, you can relive that experience every time you are greeted by a need for computation.

### 5/5 — My Go-To Calculator!!!!

*2026-02-15*

This app is so good that I almost don’t miss my old 48.  The haptic feedback upgrade was a great addition.  Love that this still works on IOS18.2.

### 5/5 — Fantastic calculator

*2026-01-27, version 1.0.8*

This is my go to calculator, and the best RPN calculator app I’ve tried.

### 5/5 — Just works!

*2026-01-27, version 1.0.8*

Grew up using RPN calculators and this one works well without any fuss.  I’ve used this calculator for years now and use it for any hand calculations I need.

### 5/5 — Best RPN Calculator

*2026-01-19*

I've been using this app for a few years across a couple phones now and it's still the best one I've tried. Well worth the money. Fully functional no-frills interface that works smoothly. 
This is my main calculator for work and home (engineering work, quick calculations that don't warrant writing a script or cracking open matlab)

### 5/5 — Great HP48 Reimagined

*2025-12-18, version 1.0.8*

This is the best HP48 RPN style calculator for iOS. Highly recommended if you love RPN and the venerable 48.

### 5/5 — Best RPN iOS calculator

*2025-11-27*

I’ve tried several free versions. I read the reviews and figured this one was worth the $4 risk.

No jankyness / bad UI. Mimics my old 48GX pretty well (minus the graphing features). Everything works as expected!

I don’t mind paying for software, especially if it motivates the developer to continue porting the app to each iOS release— (historically, a lot of my freeware apps have lost modern iOS support whenever Apple deprecates an old feature.)

## Frequently asked questions about RPN Calculator 48

### What is RPN Calculator 48?

RPN Calculator 48 is a scientific calculator application that utilizes Reverse Polish Notation (RPN) for calculations. It aims to provide a polished and functional alternative to the default calculator app on your device, inspired by the ergonomics of HP's 48-series calculators.

### What are the key features of RPN Calculator 48?

Key features include full scientific calculator functionality, RPN input method, swipe gestures for undo and redo operations, a large and easy-to-read display, a 100-entry stack, 6 memory buttons (A-F), and over 50 levels of undo/redo. The app also saves its state when you exit.

### How much does RPN Calculator 48 cost?

RPN Calculator 48 is a paid application. There are no in-app purchases or advertisements within the app, offering a straightforward purchase model for its full functionality.

### Is RPN Calculator 48 compatible with my device?

While specific compatibility details are not provided in the description, RPN Calculator 48 is designed for Apple devices, as indicated by its comparison to Apple's calculator app and its developer's other Apple-focused applications. It is likely compatible with recent versions of iOS.

### What are common use cases for RPN Calculator 48?

This app is ideal for students, engineers, scientists, and anyone who prefers or requires the RPN input method for complex mathematical and scientific calculations. Its extensive undo/redo features and clear display make it suitable for detailed problem-solving.

## Version history (last 5 releases)

### 1.0.8 — 2025-02-04

- Added support for hardware keyboards
- Added an option for haptic feedback in the main menu

### 1.0.7 — 2019-12-11

- The "LOGx" button was incorrectly labeled "LOGy". Fixed.

### 1.0.6 — 2019-11-27

- Added support for all current iPhone screen sizes and shapes
- Updated the keyboard sounds to match the current iOS sounds
- Now you can adjust the sound volume with the standard volume up/down buttons instead of a slider in the settings menu
- Added scientific and engineering notation
- Improved fixed notation: if a number is too big or too small to display, it's automatically displayed using scientific notation

### 1.0.5 — 2015-10-01

- Native support for the iPhone 6 and 6 Plus screen resolutions
- Fixes an incompatibility with iOS 9

### 1.0.4 — 2013-12-12

- Updated for iOS 7
- New "flat" icon to match iOS 7's design language

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## More apps by Tom Kerrigan

- [Chess - tChess Pro](https://appshunter.io/ios/app/chess-tchess-pro/id295445501)
- [Chess - tChess Lite](https://appshunter.io/ios/app/chess-tchess-lite/id296756437)
- [Chess - Learn Chess](https://appshunter.io/ios/app/chess-learn-chess/id305309870)
- [PopGroup](https://appshunter.io/ios/app/popgroup/id318974349)
- [PopGroup Lite](https://appshunter.io/ios/app/popgroup-lite/id318975161)
- [Chess - tChess Pro (Int'l)](https://appshunter.io/ios/app/chess-tchess-pro-intl/id333297414)

All apps by Tom Kerrigan: https://appshunter.io/developer/295445504

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*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 2026-08-26.*