# Free42 vs Retro 15C

The clearest difference is rating: Free42 at 4.8 against Retro 15C's 4.3. Free42 also leads on update cadence (every 9 days vs every 53 months) and review sentiment (94% vs 76%). Retro 15C's advantage is iOS requirement (8.0 vs 15.0). On price, ratings volume, ads and in-app purchases there is nothing between them.

Both are free to download. Neither carries in-app purchases, so what you see is what you pay.

Free42 holds the better App Store score, 4.8 against 4.3. Both are backed by a comparable volume of ratings — 287 and 233 respectively. Written reviews point the same way: 94% of Free42's written reviews are positive against 76% of Retro 15C's.

Free42 ships an update every 9 days, Retro 15C every 53 months. Both last shipped on October 26, 2026.

## The numbers

| Metric | Free42 | Retro 15C |
| --- | --- | --- |
| Price | Free | Free |
| Rating | **[4.8 (287 ratings)](https://appshunter.io/ios/app/free42/id337692629/reviews)** | [4.3 (233 ratings)](https://appshunter.io/ios/app/retro-15c/id583559000/reviews) |
| Number of ratings | **287** | 233 |
| Positive reviews | **94.4% of reviews** | 76.1% of reviews |
| In-app purchases | No | No |
| Ads | No | No |
| Update frequency | **Every 9 days** | Every 53 months |
| Monetization | Free | Free |
| Size | 9 MB | 5 MB |
| Requires iOS | 15.0 | **8.0** |
| Devices | **iPhone, iPad, iPod** | iPhone, iPod |
| Age rating | 4+ | 4+ |
| Developer | [Thomas Okken](https://appshunter.io/developer/337692632) | [Greg Hewgill](https://appshunter.io/developer/517923493) |

## What reviewers say

### Free42

[App page](https://appshunter.io/ios/app/free42/id337692629)

This application is a faithful re-implementation of the HP-42S scientific calculator and its associated printer. It offers full functionality without requiring original HP ROM images and is an open-source project.

**Highlights:** HP-42S calculator simulation, HP-82240 printer simulation, Open source project, No HP ROM required, Complete rewrite

**Features:** Vision Pro support

**In-app purchases:** none

**What reviewers like**

- 🚀 Faithful reproduction of HP42S
- 👍 Identical to physical calculator
- 👍 Runs all original programs
- 👍 Convenient to have on phone
- 👍 Haptic feedback on button presses

**What reviewers complain about**

- 🐛 Screen not filling entire display on newer devices
- 🔇 Configurable key click sound missing
- 🔇 Lack of loud click sound feedback

**Reported bugs**

- Occasional issues with Solver function
- Store and Recall functions not working properly

**Requested features**

- Display all registers (X, Y, Z, T, Last X) simultaneously
- Ability to share/transfer programs between devices
- Improved use of screen real estate on larger displays


### Retro 15C

[App page](https://appshunter.io/ios/app/retro-15c/id583559000)

This app emulates a classic RPN scientific calculator, offering advanced features like complex number arithmetic, matrix calculations, and programmability. It provides a functional and complex tool reminiscent of 1980s calculators.

**Highlights:** Complex number arithmetic, Matrix calculations, Numerical root finder, Numerical integration, Statistical functions, Programmable

**Features:** macOS Compatibility

**In-app purchases:** none

**What reviewers like**

- 🚀 Lightning-fast calculator
- 👍 Authentic look and feel of HP 15C
- 🚀 Faster than real HP 15C
- 👍 Excellent RPN emulation
- 👍 Familiar interface for HP 15C users

**What reviewers complain about**

- 🐛 Doesn't save settings, programs, or memory
- 🐛 No key press feedback or sound
- 🐛 Blinking display issue with large calculations
- 🐛 Bugs with HMS conversions
- 🐛 Can't close app on newer iPhones

**Reported bugs**

- Blinking display with large calculations
- Bugs with HMS conversions
- Inability to close app on newer iPhones
- Stopped working with iOS 14 updates

**Requested features**

- Add haptic feedback on key presses
- Implement continuous memory to save settings and programs
- Add portrait mode option
- Improve compatibility with newer iOS versions
- Add copy/paste functionality for stack and registers


## Frequently asked questions

### Is Free42 free?

Free42 is free to download, with no in-app purchases.

### Is Retro 15C free?

Retro 15C is free to download, with no in-app purchases.

### Which has better reviews, Free42 or Retro 15C?

Free42 is rated higher. Free42 averages 4.8 out of 5 from 287 ratings, while Retro 15C averages 4.3 from 233 ratings.

### Do Free42 or Retro 15C have ads?

Neither Free42 nor Retro 15C shows ads.

### Which is updated more often, Free42 or Retro 15C?

Free42 ships an update every 9 days, and Retro 15C every 53 months. Most recently, Free42 was updated on October 26, 2026 and Retro 15C on October 26, 2026.

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*Compared by [AppsHunter](https://appshunter.io/) from daily US App Store data. Review summaries are generated from verbatim App Store reviews.*