# System 911 vs Happy Kitty Calculator

The clearest difference is in-app purchases: System 911 at none against Happy Kitty Calculator's 1. System 911 also leads on iOS requirement (9 vs 15.6). Happy Kitty Calculator's advantage is update cadence (every 3 weeks vs every 6 weeks). On price, ads and device support there is nothing between them.

Both are free to download. Happy Kitty Calculator sells 1 one-off in-app purchase. System 911 asks for nothing beyond the download.

System 911 ships an update every 6 weeks, Happy Kitty Calculator every 3 weeks. Both last shipped on October 25, 2026.

## The numbers

| Metric | System 911 | Happy Kitty Calculator |
| --- | --- | --- |
| Price | Free | Free |
| In-app purchases | **No** | Yes |
| Ads | No | No |
| Update frequency | Every 6 weeks | **Every 3 weeks** |
| Size | 29 MB | 59 MB |
| Requires iOS | **9** | 15.6 |
| Devices | iPhone, iPod | iPhone, iPod |
| Age rating | 4+ | 4+ |
| Developer | [学新 黄](https://appshunter.io/developer/1450715299) | [HUA-TENG HUANG](https://appshunter.io/developer/1780056727) |

## What reviewers say

### System 911

[App page](https://appshunter.io/ios/app/system-911/id1497419202)

**Features:** macOS Compatibility

**In-app purchases:** none


### Happy Kitty Calculator

[App page](https://appshunter.io/ios/app/happy-kitty-calculator/id6739179959)

**Features:** Family Sharing, Vision Pro support

**In-app purchases (1)**

| Purchase | Price | Billing |
| --- | --- | --- |
| One-time purchase. | $2.99 | one-time |


## Frequently asked questions

### Is System 911 free?

System 911 is free to download, with no in-app purchases.

### Is Happy Kitty Calculator free?

Happy Kitty Calculator is free to download, with in-app purchases available.

### Do System 911 or Happy Kitty Calculator have ads?

Neither System 911 nor Happy Kitty Calculator shows ads.

### Which is updated more often, System 911 or Happy Kitty Calculator?

System 911 ships an update every 6 weeks, and Happy Kitty Calculator every 3 weeks. Most recently, System 911 was updated on October 25, 2026 and Happy Kitty Calculator on October 25, 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.*