# Calx: Stack calculator

> RPN calculator app with gestural interaction and customizable interface. (iPhone/iPad app by Daniel Clelland.)

- Source: https://appshunter.io/ios/app/calx-stack-calculator/id928929230 (this page in markdown: same URL + `.md`)
- Developer: [Daniel Clelland](https://appshunter.io/developer/912177584)
- Category: Utilities, Productivity
- Price: $0.99
- Rating: 5.00/5 from 2 App Store ratings · 4 written reviews indexed
- Age rating: 4+
- Requires: iOS 12.0 · 4 MB
- Languages: American English, French (France), German (Germany), Japanese, Chinese (Simplified, China), European Spanish
- Released: 2015-04-26
- Data updated: 2026-08-12
- Monetization: paid
- User reviews in markdown: https://appshunter.io/ios/app/calx-stack-calculator/id928929230/reviews.md

## What is Calx?

CALX is an RPN calculator — a calculator designed to work with a list of numbers.

This means that instead of just typing an equation into your calculator, you push numbers onto a stack, and then apply operations to the lowermost numbers in the stack.

It's bizarre, but it makes sense once it clicks.

If this all sounds confusing, don't worry! CALX comes with a guided tutorial which will get you up to speed in three minutes.

Features:

• Gestural interaction: Manipulate your data with simple, intuitive gestures.
• Multiple keypads: CALX features an array of basic, scientific, and statistical functions.
• Customization: Select from different fonts and colours to find a combination that works for you.

## Key features

- Reverse Polish Notation (RPN)
- Gestural interaction
- Multiple keypads (basic, scientific, statistical)
- Customizable fonts and colors
- Guided tutorial

## Recent user reviews (4 of 4)

All indexed reviews: https://appshunter.io/ios/app/calx-stack-calculator/id928929230/reviews.md

### 5/5 — A delightful and essential reimagining of RPN

*2024-11-23*

A miniature masterpiece, Calx rethinks the RPN or stack calculator from the ground up, making great use of the touch interface -- swipe left to reveal statistics, right to reveal the scientific functions, and you can swipe any point in the stack to delete that line and have the rest sink down like tetris blocks. Unlike other RPN calculator apps that seek to visually emulate the HP calculators of the 1970s and 80s that we all love, Calx is its own thing, a smooth and simple interface for crunching numbers. I use it on iPad where it stays well behaved and a suitable size (not expanding across the whole screen with huge buttons like Apple's IOS18 calculator). The only thing I could ask for is is to add split screen capability so one can calculate while looking at a source document where the numbers are rather than hopping back and forth ...

### 5/5 — Exactly what I was looking for.

*2020-08-18*

I’ve been looking for a stack-based calculator like this for quite a while, resembling how RPL (not RPN) calculators like the HP48 used to work.
If you have never used a calculator like this, give
it a try. This type of calculator becomes so addictive that you’ll never want to use anything else.

### 5/5 — Fast and easy RPN calculator

*2020-06-28*

The main advantage of RPN is speed and efficiency, and CALX makes RPN simple and intuitive to use. I was hesitant to spend money on a calculator considering how many free alternatives there are, but I’m glad I did. For simple calculations CALX is faster to use than my (physical) graphics calculators, and unlike RPN calculator apps that emulate old HP models there’s no archaic “X, Y, Z, T” stack behaviour to think about, either. 
The swipe behaviour of CALX makes best use of the touch screen, and you can swipe the controls to show other functions (including super-handy statistical calculations), swipe on individual items in the stack to remove them, and swipe up to clear everything. Worth the few dollars it costs.

### 5/5 — Absolutely perfect

*2017-05-05*

Takes a scary concept and makes it beautiful and simple. The only calculator I'll ever need. Wonderful job!

## Frequently asked questions about Calx

### What is Calx's price?

Calx is a paid application, priced at $0.99. This one-time purchase grants you access to all its features.

### Does Calx have ads?

No, Calx is ad-free. As a paid application, it does not contain any advertisements, allowing for an uninterrupted user experience.

### What devices does Calx support?

Calx is available for iPhone and iPod devices. It is designed to run on iOS operating systems.

### How often is Calx updated?

The latest version of Calx was released on October 9, 2023. While specific update frequency isn't detailed, it has received updates since its initial release in 2015.

### What is the age rating for Calx?

Calx has an age rating of 4+. This indicates it is suitable for users of all ages, with no mature content.

### How does Calx teach RPN?

Calx includes a guided tutorial designed to get users up to speed with RPN in approximately three minutes. This feature helps new users understand the unique calculation method.

### What kind of keypads does Calx offer?

Calx features multiple keypads, including basic, scientific, and statistical functions. This array of options caters to a wide range of calculation needs.

### What do users like about Calx?

Based on the available rating, users have given Calx a perfect 5.0 stars. This suggests a high level of user satisfaction with its functionality and design.

## Version history (last 5 releases)

### 1.2.3 — 2023-10-09

- iPhone 15 bugfixes

### 1.2.1 — 2019-10-13

- Fix font issues on iOS 13

### 1.2 — 2019-05-02

- iPhone X support

### 1.1 — 2016-06-06

- iOS 9 font support

### 1.0 — 2015-04-26

No release notes.

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| [CalcKit](https://appshunter.io/ios/app/calckit/id321006774) | — | Free | Utilities |
| [RPN-Calc](https://appshunter.io/ios/app/rpn-calc/id6464329997) | — | $4.99 | Utilities |

## More apps by Daniel Clelland

- [Howl: A formant synthesizer](https://appshunter.io/ios/app/howl-a-formant-synthesizer/id1067562312)

All apps by Daniel Clelland: https://appshunter.io/developer/912177584

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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 2026-08-12.*