# ThetaCalc

> RPN calculator with user-programmable JavaScript functions and equations. (iPhone/iPad app by Felix Stehli.)

- Source: https://appshunter.io/ios/app/thetacalc/id1521614636 (this page in markdown: same URL + `.md`)
- Developer: [Felix Stehli](https://appshunter.io/developer/1521614638)
- Category: Utilities
- Price: Free
- Rating: 4.25/5 from 4 App Store ratings · 3 written reviews indexed
- Age rating: 4+
- Requires: iOS 17.6 · 1 MB
- Languages: English
- Released: 2020-07-06
- Data updated: 2026-06-01
- Monetization: free
- User reviews in markdown: https://appshunter.io/ios/app/thetacalc/id1521614636/reviews.md

## What is ThetaCalc?

ThetaCalc is a RPN (Reverse Polish Notation) calculator which can be extended by functions and equations programmed by the user in JavaScript.

## Key features

- Reverse Polish Notation (RPN) calculator
- User-programmable functions
- JavaScript equation support
- Extensible functionality

## Recent user reviews (3 of 3)

All indexed reviews: https://appshunter.io/ios/app/thetacalc/id1521614636/reviews.md

### 5/5 — Like HP42 or DM42 with Javascript

*2022-08-08*

This calculator is an RPN calculator like the HP42S or DM42 but instead of RPL it uses Javascript for its programming model. This is seriously amazing! I have a bunch of other RPN calculators for iOS and this one blows them all out of the water in every way.

### 5/5 — Wow

*2022-03-15*

Didn’t take long to figure out, seems to go ok, like the JavaScript code feature +  clear examples. A very tuneable calculator (3,2,1++=) rpn. Luv it. Luv it.

### 5/5 — Well thought out JavaScript extensible RPN calculator

*2020-12-09*

There’s no end to what you can do with this calculator!

If you need a calculator to do something unique, you can probably get it done with ThetaCalc.

I wanted to generate a specialized flightplan for an online flight simulator. No problem, ThetaCalc was up to the task. Then for maximum usability,  I needed to generate the output as an XML file. Once again, no problem.

It’s so sweet to have this programmability in the palm of your hand.

## Frequently asked questions about ThetaCalc

### What is ThetaCalc?

ThetaCalc is a free utility app that functions as a Reverse Polish Notation (RPN) calculator. It allows users to extend its capabilities by programming custom functions and equations using JavaScript.

### What devices does ThetaCalc support?

ThetaCalc is available for iPhone and iPad devices. It is designed for users who need a powerful and customizable calculator on their Apple mobile devices.

### How often is ThetaCalc updated?

The latest version of ThetaCalc is 1.9, released on September 16, 2025. While specific update frequency isn't detailed, the app has received updates since its initial release on July 6, 2020.

### Is ThetaCalc suitable for children?

ThetaCalc has an age rating of 4+, making it suitable for a wide range of users. Its utility functions are generally appropriate for educational and personal use.

### Can I program my own functions in ThetaCalc?

Yes, a key feature of ThetaCalc is its ability to be extended by functions and equations programmed by the user in JavaScript. This allows for highly customized calculations.

### Does ThetaCalc have ads?

No, ThetaCalc is completely ad-free. As a free application, it does not display any advertisements, providing an uninterrupted user experience.

### What is the user sentiment for ThetaCalc?

ThetaCalc has a positive user sentiment, reflected in its rating of 4.3 stars from 4 ratings. This indicates that users who have reviewed the app generally find it to be a useful and well-functioning utility.

### What is the price of ThetaCalc?

ThetaCalc is available for free. There are no costs associated with downloading or using the core functionality of the RPN calculator and its JavaScript programming features.

## Version history (last 5 releases)

### 2.0 — 2026-05-17

Improved JS editor (syntax highlighting, auto indenting)

### 1.9 — 2025-09-16

Minor corrections, additional display theme.

### 1.8 — 2025-03-11

Changed rounding from bankers algorithm to standard rounding (half up)
Option to set font size of X
Two new calculator themes

### 1.7 — 2025-01-24

Slightly improved handling of JavaScript errors
Calculator color themes
Increased number of user assignable buttons
Minor improvements and bug fixes

### 1.6 — 2024-10-21

Minor bug fixes and improvements.

## Apps similar to ThetaCalc

| App | Rating | Price | Category |
| --- | --- | --- | --- |
| [RLM-10CX](https://appshunter.io/ios/app/rlm-10cx/id6466089794) | 5.0 (1) | Free | Utilities |
| [Calccis](https://appshunter.io/ios/app/calccis/id6446233205) | — | Free | Utilities |
| [Complex RPN Calculator](https://appshunter.io/ios/app/complex-rpn-calculator/id291826330) | 3.8 (22) | Free | Utilities |
| [RCL-57](https://appshunter.io/ios/app/rcl-57/id1621959742) | — | Free | Utilities |
| [Dozecal](https://appshunter.io/ios/app/dozecal/id1521160089) | 4.0 (4) | Free | Utilities |
| [SwiftRPN](https://appshunter.io/ios/app/swiftrpn/id6470951024) | — | Free | Utilities |

## More apps by Felix Stehli

- [PentoCruncher](https://appshunter.io/ios/app/pentocruncher/id1609954103)
- [Lettello](https://appshunter.io/ios/app/lettello/id6449615306)
- [JassMax](https://appshunter.io/ios/app/jassmax/id6752518180)

All apps by Felix Stehli: https://appshunter.io/developer/1521614638

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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 2026-06-01.*