# Retro 15C vs RLM

The clearest difference is rating: Retro 15C at 4.3 against RLM's 3.1. Retro 15C also leads on in-app purchases (none vs 4) and ratings volume (233 vs 7). RLM's advantage is update cadence (every 5 weeks vs every 53 months). On price, ads and device support there is nothing between them.

Both are free to download. RLM sells 4 in-app purchases, starting at $0.49 per month. Retro 15C asks for nothing beyond the download.

Retro 15C holds the better App Store score, 4.3 against 3.1. That said, the two scores are not equally well evidenced: Retro 15C has 233 ratings behind it against 7, so its average is the more settled of the two. Written reviews point the same way: 76% of Retro 15C's written reviews are positive against 67% of RLM's.

Retro 15C ships an update every 53 months, RLM every 5 weeks. The most recent releases landed on October 26, 2026 and October 24, 2026 respectively.

## The numbers

| Metric | Retro 15C | RLM |
| --- | --- | --- |
| Price | Free | Free |
| Rating | **[4.3 (233 ratings)](https://appshunter.io/ios/app/retro-15c/id583559000/reviews)** | [3.1 (7 ratings)](https://appshunter.io/ios/app/rlm-11cx/id1630739014/reviews) |
| Number of ratings | **233** | 7 |
| Positive reviews | **76.1% of reviews** | 66.7% of reviews |
| In-app purchases | **No** | Yes |
| Ads | No | No |
| Update frequency | Every 53 months | **Every 5 weeks** |
| Monetization | **Free** | Free with in-app purchases |
| Size | 5 MB | 6 MB |
| Requires iOS | **8.0** | 15.0 |
| Devices | iPhone, iPod | **iPhone, iPad, iPod** |
| Age rating | 4+ | 4+ |
| Developer | [Greg Hewgill](https://appshunter.io/developer/517923493) | [R.L.M. Software](https://appshunter.io/developer/289639238) |

## 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


### RLM

[App page](https://appshunter.io/ios/app/rlm-11cx/id1630739014)

This app is a scientific and programmable calculator designed for science and engineering, replicating the functionality of the HP-11C. It offers extensive features for finance, business, statistics, complex numbers, and unit conversions, with a programmable interface for custom calculations.

**Highlights:** Finance calculations (amortization, bond price, Black-Scholes), Business functions (break-even, currency exchange), Statistical analysis (regression, probability distributions), Scientific functions (complex numbers, logarithms, trigonometry), Unit and currency conversions, Programmable interface for custom scripts, Equation solver

**Features:** macOS Compatibility, Vision Pro support

**In-app purchases (4)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Monthly Subscription | $0.49 | per month |
| Semi-Annual Subscription | $2.99 | per 6 months |
| Annual Subscription | $5.99 | per year |
| Lifetime Purchase | $9.99 | one-time |


## Frequently asked questions

### Is Retro 15C free?

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

### Is RLM free?

RLM is free to download, with in-app purchases available.

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

Retro 15C is rated higher. Retro 15C averages 4.3 out of 5 from 233 ratings, while RLM averages 3.1 from 7 ratings.

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

Neither Retro 15C nor RLM shows ads.

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

Retro 15C ships an update every 53 months, and RLM every 5 weeks. Most recently, Retro 15C was updated on October 26, 2026 and RLM on October 24, 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.*