# Pool vs KinLetter

The clearest difference is price: KinLetter at Free against Pool's $4.99. KinLetter also leads on update cadence (every 6 days vs every 5 weeks). Pool's advantage is device support (3 vs 1). On ads, in-app purchases and iOS requirement there is nothing between them.

KinLetter is free to download; Pool costs $4.99 up front. Neither carries in-app purchases, so what you see is what you pay.

Pool ships an update every 5 weeks, KinLetter every 6 days. The most recent releases landed on September 28, 2026 and September 14, 2026 respectively.

## The numbers

| Metric | Pool | KinLetter |
| --- | --- | --- |
| Price | $4.99 | **Free** |
| Rating | **[4.2 (629 ratings)](https://appshunter.io/ios/app/pool-calculator/id412876581/reviews)** | — |
| Number of ratings | **629** | — |
| Positive reviews | 21.8% of reviews | — |
| In-app purchases | No | No |
| Ads | No | No |
| Update frequency | Every 5 weeks | **Every 6 days** |
| Monetization | Free | — |
| Size | 17 MB | 72 MB |
| Requires iOS | **15.1** | 16.4 |
| Devices | **iPhone, iPad, iPod** | iPhone |
| Age rating | 4+ | 12+ |
| Developer | [Pool and Spa Resources, LLC](https://appshunter.io/developer/1358030201) | [Version2Labs, LLC](https://appshunter.io/developer/6775683410) |

## What reviewers say

### Pool

[App page](https://appshunter.io/ios/app/pool-calculator/id412876581)

This app simplifies swimming pool and hot tub chemistry maintenance by performing all necessary calculations. It provides clear instructions on chemical dosages to maintain balanced, clear water, eliminating the need for complex charts and formulas.

**Highlights:** Chemical dosage calculations, Pool volume calculation, Chemical effects analysis, Customizable chemical ranges, Offline functionality

**Features:** Vision Pro support

**In-app purchases:** none

**What reviewers like**

- 💡 Useful pool chemistry calculator
- 🚀 Makes pool maintenance easy
- 👍 Provides chemical dosage recommendations
- 🔍 Helpful 'Effects' tool to understand chemical impacts

**What reviewers complain about**

- 🐛 Accuracy issues with certain chemical calculations
- 🔍 Confusing or outdated chemical names
- 🔍 Limited customization options
- 🐛 Crashes and compatibility issues with newer iOS versions

**Reported bugs**

- App crashes on launch for many users
- Keyboard issues preventing data entry
- Incorrect chemical effect information (e.g. soda ash)
- Volume calculation not updating properly

**Requested features**

- Ability to save and track test history
- Support for multiple pools/spas
- Metric-only unit support
- More detailed chemical dosage information (e.g. weight-based)


### KinLetter

[App page](https://appshunter.io/ios/app/kinletter/id6775683408)

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

**In-app purchases:** none


## Frequently asked questions

### Is Pool free?

Pool costs $4.99, with no in-app purchases.

### Is KinLetter free?

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

### Do Pool or KinLetter have ads?

Neither Pool nor KinLetter shows ads.

### Which is updated more often, Pool or KinLetter?

Pool ships an update every 5 weeks, and KinLetter every 6 days. Most recently, Pool was updated on September 28, 2026 and KinLetter on September 14, 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.*