# Retro 15C vs Plus42

The clearest difference is price: Retro 15C at Free against Plus42's $9.99. Retro 15C also leads on iOS requirement (8.0 vs 12.0). Plus42's advantage is rating (4.9 vs 4.3) and update cadence (weekly vs every 53 months). On ratings volume, ads, in-app purchases and monetization model there is nothing between them.

Retro 15C is free to download; Plus42 costs $9.99 up front. Neither carries in-app purchases, so what you see is what you pay.

Plus42 holds the better App Store score, 4.9 against 4.3. Both are backed by a comparable volume of ratings — 212 and 79 respectively. Written reviews point the same way: 76% of Retro 15C's written reviews are positive against 92% of Plus42's.

Retro 15C ships an update every 53 months, Plus42 weekly. The most recent releases landed on October 7, 2026 and October 13, 2026 respectively.

## The numbers

| Metric | Retro 15C | Plus42 |
| --- | --- | --- |
| Price | **Free** | $9.99 |
| Rating | [4.3 (212 ratings)](https://appshunter.io/ios/app/retro-15c/id583559000/reviews) | **[4.9 (79 ratings)](https://appshunter.io/ios/app/plus42/id1597963622/reviews)** |
| Number of ratings | **212** | 79 |
| Positive reviews | 76.1% of reviews | **92.3% of reviews** |
| In-app purchases | No | No |
| Ads | No | No |
| Update frequency | Every 53 months | **Weekly** |
| Monetization | Free | Free |
| Size | 5 MB | 11 MB |
| Requires iOS | **8.0** | 12.0 |
| Devices | iPhone, iPod | **iPhone, iPad, iPod** |
| Age rating | 4+ | 4+ |
| Developer | [Greg Hewgill](https://appshunter.io/developer/517923493) | [Thomas Okken](https://appshunter.io/developer/337692632) |

## What reviewers say

### 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


### Plus42

[App page](https://appshunter.io/ios/app/plus42/id1597963622)

This advanced scientific calculator simulates the classic HP-42S RPN calculator with enhanced features. It offers algebraic expressions, unit conversions, directories for storage, a larger resizable display, financial functions, and 2D plotting with integral and root finding.

**Highlights:** HP-42S RPN calculator simulation, Algebraic expressions, Attached units and conversions, Program and variable directories, Resizable 8-row, 22-column display, Time value of money and amortization, 2D function plotting with zoom and pan

**Features:** Vision Pro support

**In-app purchases:** none


## Frequently asked questions

### Is Retro 15C free?

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

### Is Plus42 free?

Plus42 costs $9.99, with no in-app purchases.

### Which has better reviews, Retro 15C or Plus42?

Plus42 is rated higher. Retro 15C averages 4.3 out of 5 from 212 ratings, while Plus42 averages 4.9 from 79 ratings.

### Do Retro 15C or Plus42 have ads?

Neither Retro 15C nor Plus42 shows ads.

### Which is updated more often, Retro 15C or Plus42?

Retro 15C ships an update every 53 months, and Plus42 weekly. Most recently, Retro 15C was updated on October 7, 2026 and Plus42 on October 13, 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.*