# Scientific Calculator Plus 991 vs Sentry

The clearest difference is in-app purchases: Sentry at none against Scientific Calculator Plus 991's 4. Sentry also leads on ads (none vs shown) and iOS requirement (13.0 vs 15). Scientific Calculator Plus 991's advantage is update cadence (fortnightly vs every 19 months) and device support (4 vs 2). On price there is nothing between them.

Both are free to download. Scientific Calculator Plus 991 sells 4 in-app purchases, starting at $1.99 per month. Sentry asks for nothing beyond the download.

Scientific Calculator Plus 991 ships an update fortnightly, Sentry every 19 months. Both last shipped on October 27, 2026.

## The numbers

| Metric | Scientific Calculator Plus 991 | Sentry |
| --- | --- | --- |
| Price | Free | Free |
| Rating | **[4.7 (13K ratings)](https://appshunter.io/ios/app/scientific-calculator-plus-991/id1449106995/reviews)** | — |
| Number of ratings | **13K** | — |
| Positive reviews | 91.7% of reviews | — |
| In-app purchases | Yes | **No** |
| Ads | Yes | **No** |
| Update frequency | **Fortnightly** | Every 19 months |
| Monetization | Free with in-app purchases | — |
| Size | 169 MB | 28 MB |
| Requires iOS | 15 | **13.0** |
| Devices | **iPhone, iPad, iPod, Mac** | iPhone, iPod |
| Age rating | 12+ | 4+ |
| Developer | [Tran Duy](https://appshunter.io/developer/1449106994) | [S. B. ELECTRONIC SYSTEMS LIMITED](https://appshunter.io/developer/1230083095) |

## What reviewers say

### Scientific Calculator Plus 991

[App page](https://appshunter.io/ios/app/scientific-calculator-plus-991/id1449106995)

This app is a powerful scientific calculator with graphing capabilities, a formula library, and a unit converter. It offers natural display input, advanced math functions for algebra, calculus, and statistics, and supports various number bases and formats.

**Highlights:** Natural display input, Graphing module, Formula library, Unit and currency converter, Algebra and calculus tools, Matrix and vector operations, Statistical calculations

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

**In-app purchases (4)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Calculator month subscription | $1.99 | per month |
| Calculator yearly subscription | $3.99 | per year |
| Calculator Premium | $5.99 | one-time |
| Calculator Pro | $5.99 | one-time |

**What reviewers like**

- 👍 Intuitive and easy to use
- 🚀 Powerful and feature-rich
- 💡 Customizable interface and settings
- 🔍 Extensive library of formulas and equations
- ⚙️ Handles complex math and scientific functions well

**What reviewers complain about**

- 🐛 Occasional bugs and input issues
- 🔀 Confusing layout and button placement
- 💰 Some advanced features locked behind paywall

**Reported bugs**

- Keyboard input stops working after switching screens
- Incorrect calculation results for certain operations
- App crashes on some devices after recent update

**Requested features**

- Add option to change display font and color
- Improve cursor control and editing capabilities
- Implement auto-simplification for complex expressions
- Add more handwriting font options
- Expand graphing and equation solving features


### Sentry

[App page](https://appshunter.io/ios/app/sentry/id6446584580)

**Features:** Apple Wallet, Vision Pro support

**In-app purchases:** none


## Frequently asked questions

### Is Scientific Calculator Plus 991 free?

Scientific Calculator Plus 991 is free to download, with in-app purchases available.

### Is Sentry free?

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

### Do Scientific Calculator Plus 991 or Sentry have ads?

Scientific Calculator Plus 991 shows ads; Sentry does not.

### Which is updated more often, Scientific Calculator Plus 991 or Sentry?

Scientific Calculator Plus 991 ships an update fortnightly, and Sentry every 19 months. Most recently, Scientific Calculator Plus 991 was updated on October 27, 2026 and Sentry on October 27, 2026.

---

*Compared by [AppsHunter](https://appshunter.io/) from daily US App Store data. Review summaries are generated from verbatim App Store reviews.*