# |RPN| Scientific Calculator vs HP

The clearest difference is price: HP at Free against |RPN| Scientific Calculator's $0.99. HP also leads on rating (4.6 vs 2.3) and review sentiment (100% vs 60%). |RPN| Scientific Calculator's advantage is device support (4 vs 1). On update cadence, ads, in-app purchases and iOS requirement there is nothing between them.

HP is free to download; |RPN| Scientific Calculator costs $0.99 up front. Neither carries in-app purchases, so what you see is what you pay.

HP holds the better App Store score, 4.6 against 2.3. That said, the two scores are not equally well evidenced: HP has 62 ratings behind it against 3, so its average is the more settled of the two. Written reviews point the same way: 60% of |RPN| Scientific Calculator's written reviews are positive against 100% of HP's.

|RPN| Scientific Calculator ships an update fortnightly, HP every 11 days. The most recent releases landed on October 24, 2026 and October 30, 2026 respectively.

## The numbers

| Metric | |RPN| Scientific Calculator | HP |
| --- | --- | --- |
| Price | $0.99 | **Free** |
| Rating | [2.3 (3 ratings)](https://appshunter.io/ios/app/rpn-scientific-calculator/id1069467997/reviews) | **[4.6 (62 ratings)](https://appshunter.io/ios/app/hp-35/id6738010641/reviews)** |
| Number of ratings | 3 | **62** |
| Positive reviews | 60.0% of reviews | **100.0% of reviews** |
| In-app purchases | No | No |
| Ads | No | No |
| Update frequency | Fortnightly | **Every 11 days** |
| Monetization | Paid | **Free** |
| Size | 2 MB | 2 MB |
| Requires iOS | **16** | 17.2 |
| Devices | **iPhone, iPad, iPod, Mac** | iPhone |
| Age rating | 4+ | 4+ |
| Developer | [Bradley Smith](https://appshunter.io/developer/1069467996) | [Enrique Haro](https://appshunter.io/developer/1778874870) |

## What reviewers say

### |RPN| Scientific Calculator

[App page](https://appshunter.io/ios/app/rpn-scientific-calculator/id1069467997)

This calculator app uses Reverse Polish Notation for powerful calculations. It offers customizable color schemes, layouts, and online help, designed for flexibility and usability. All features are unlocked with a one-time purchase.

**Highlights:** Reverse Polish Notation (RPN), Viewable stack, Selectable portrait/landscape layouts, Customizable color schemes, Online visual help, No ads or in-app purchases

**Features:** Vision Pro support

**In-app purchases:** none


### HP

[App page](https://appshunter.io/ios/app/hp-35/id6738010641)

Emulates classic Hewlett Packard RPN scientific calculators from the 1970s. Experience the original HP-35, HP-45, and HP-21 models on your iPhone.

**Highlights:** RPN calculator emulation, HP-35 model, HP-45 model, HP-21 model, Classic scientific calculator interface

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

**In-app purchases:** none


## Frequently asked questions

### Is |RPN| Scientific Calculator free?

|RPN| Scientific Calculator costs $0.99, with no in-app purchases.

### Is HP free?

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

### Which has better reviews, |RPN| Scientific Calculator or HP?

HP is rated higher. |RPN| Scientific Calculator averages 2.3 out of 5 from 3 ratings, while HP averages 4.6 from 62 ratings.

### Do |RPN| Scientific Calculator or HP have ads?

Neither |RPN| Scientific Calculator nor HP shows ads.

### Which is updated more often, |RPN| Scientific Calculator or HP?

|RPN| Scientific Calculator ships an update fortnightly, and HP every 11 days. Most recently, |RPN| Scientific Calculator was updated on October 24, 2026 and HP on October 30, 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.*