# BigSIA vs CAS_Calc

The clearest difference is in-app purchases: CAS_Calc at none against BigSIA's 1. CAS_Calc also leads on update cadence (fortnightly vs every 2 months). BigSIA's advantage is iOS requirement (11.0 vs 17.6). On price, ads and device support there is nothing between them.

Both are free to download. BigSIA sells 1 in-app purchase, starting at $19.49 per year. CAS_Calc asks for nothing beyond the download.

BigSIA ships an update every 2 months, CAS_Calc fortnightly. The most recent releases landed on November 2, 2026 and November 10, 2026 respectively.

## The numbers

| Metric | BigSIA | CAS_Calc |
| --- | --- | --- |
| Price | Free | Free |
| In-app purchases | Yes | **No** |
| Ads | No | No |
| Update frequency | Every 2 months | **Fortnightly** |
| Size | 14 MB | 17 MB |
| Requires iOS | **11.0** | 17.6 |
| Devices | **iPhone, iPad, iPod** | iPhone, iPad |
| Age rating | 4+ | 4+ |
| Developer | [Qvision, Departamento de Oftalmología](https://appshunter.io/developer/1602553646) | [Peter Hoffmann](https://appshunter.io/developer/6797644932) |

## What reviewers say

### BigSIA

[App page](https://appshunter.io/ios/app/bigsia/id1413756508)

**Features:** Vision Pro support

**In-app purchases (1)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Pro | $19.49 | per year |


### CAS_Calc

[App page](https://appshunter.io/ios/app/cas-calc/id6798420368)

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

**In-app purchases:** none


## Frequently asked questions

### Is BigSIA free?

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

### Is CAS_Calc free?

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

### Do BigSIA or CAS_Calc have ads?

Neither BigSIA nor CAS_Calc shows ads.

### Which is updated more often, BigSIA or CAS_Calc?

BigSIA ships an update every 2 months, and CAS_Calc fortnightly. Most recently, BigSIA was updated on November 2, 2026 and CAS_Calc on November 10, 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.*