# Physical Constants vs Pocket 991

The clearest difference is price: Physical Constants at Free against Pocket 991's $0.99. Physical Constants also leads on iOS requirement (12.0 vs 17.0). Pocket 991's advantage is ads (none vs shown) and update cadence (fortnightly vs every 9 months). On in-app purchases and device support there is nothing between them.

Physical Constants is free to download; Pocket 991 costs $0.99 up front. Neither carries in-app purchases, so what you see is what you pay.

Physical Constants ships an update every 9 months, Pocket 991 fortnightly. The most recent releases landed on November 1, 2026 and October 31, 2026 respectively.

## The numbers

| Metric | Physical Constants | Pocket 991 |
| --- | --- | --- |
| Price | **Free** | $0.99 |
| Rating | **[3.3 (3 ratings)](https://appshunter.io/ios/app/physical-constants-ml/id837679891/reviews)** | — |
| Number of ratings | **3** | — |
| Positive reviews | 33.3% of reviews | — |
| In-app purchases | No | No |
| Ads | Yes | **No** |
| Update frequency | Every 9 months | **Fortnightly** |
| Monetization | Ad-supported | — |
| Size | 25 MB | 12 MB |
| Requires iOS | **12.0** | 17.0 |
| Devices | **iPhone, iPad, iPod** | iPhone, iPad |
| Age rating | 4+ | 4+ |
| Developer | [Takuya Ishikawa](https://appshunter.io/developer/468311118) | [Charlie Candlish](https://appshunter.io/developer/1649541666) |

## What reviewers say

### Physical Constants

[App page](https://appshunter.io/ios/app/physical-constants-ml/id837679891)

Access a comprehensive list of physical constants, organized by category for easy searching. This app supports all AppStore languages and allows users to report corrections via email.

**Highlights:** Physical constants database, Categorized by topic, Search functionality, Multi-language support, User feedback for corrections

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

**In-app purchases:** none


### Pocket 991

[App page](https://appshunter.io/ios/app/pocket-991/id6809568813)

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

**In-app purchases:** none


## Frequently asked questions

### Is Physical Constants free?

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

### Is Pocket 991 free?

Pocket 991 costs $0.99, with no in-app purchases.

### Do Physical Constants or Pocket 991 have ads?

Physical Constants shows ads; Pocket 991 does not.

### Which is updated more often, Physical Constants or Pocket 991?

Physical Constants ships an update every 9 months, and Pocket 991 fortnightly. Most recently, Physical Constants was updated on November 1, 2026 and Pocket 991 on October 31, 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.*