# IsI Calculator vs Clock Tower

The clearest difference is device support: IsI Calculator at 4 against Clock Tower's 2. IsI Calculator also leads on iOS requirement (9.0 vs 26.0). On price, 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.

## The numbers

| Metric | IsI Calculator | Clock Tower |
| --- | --- | --- |
| Price | Free | Free |
| In-app purchases | No | No |
| Ads | No | No |
| Update frequency | Fortnightly | — |
| Size | 15 MB | 3 MB |
| Requires iOS | **9.0** | 26.0 |
| Devices | **iPhone, iPad, iPod, Apple Watch** | iPhone, Mac |
| Age rating | 4+ | 4+ |
| Developer | [Dominic Barra](https://appshunter.io/developer/891093115) | [Morgan Hunt](https://appshunter.io/developer/1539166783) |

## What reviewers say

### IsI Calculator

[App page](https://appshunter.io/ios/app/isi-calculator/id891516315)

**Features:** macOS Compatibility

**In-app purchases:** none


### Clock Tower

[App page](https://appshunter.io/ios/app/clock-tower-mm/id6792607662)

**Features:** Vision Pro support

**In-app purchases:** none


## Frequently asked questions

### Is IsI Calculator free?

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

### Is Clock Tower free?

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

### Do IsI Calculator or Clock Tower have ads?

Neither IsI Calculator nor Clock Tower shows ads.

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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.*