# Combinatorics Calculator vs ReadBay

Combinatorics Calculator and ReadBay are too close to call on the numbers: across 6 compared parameters — price, update cadence, ads and in-app purchases among them — neither pulls far enough ahead to decide it. What separates them is feature set and interface, not measurable difference.

Both are free to download. Combinatorics Calculator sells 8 one-off in-app purchases and ReadBay sells 4 in-app purchases, starting at $4.99 per month. Whichever you choose, the download price is not the number that matters.

Combinatorics Calculator ships an update every 3 weeks, ReadBay every 10 days. The most recent releases landed on October 24, 2026 and October 23, 2026 respectively.

## The numbers

| Metric | Combinatorics Calculator | ReadBay |
| --- | --- | --- |
| Price | Free | Free |
| Rating | — | **[4.8 (239 ratings)](https://appshunter.io/ios/app/readbay-book-summaries/id6499073338/reviews)** |
| Number of ratings | — | **239** |
| Positive reviews | — | 84.5% of reviews |
| In-app purchases | Yes | Yes |
| Ads | No | No |
| Update frequency | Every 3 weeks | **Every 10 days** |
| Monetization | — | Free with in-app purchases |
| Size | 180 MB | 60 MB |
| Requires iOS | **15.0** | 15.1 |
| Devices | iPhone, iPad, iPod | iPhone, iPad, iPod |
| Age rating | 4+ | 17+ |
| Developer | [Glindemann, Sennoun, Langer GbR](https://appshunter.io/developer/1024972809) | [Bange Sabastine Hwonyi](https://appshunter.io/developer/1708740698) |

## What reviewers say

### Combinatorics Calculator

[App page](https://appshunter.io/ios/app/combinatorics-calculator/id6472453602)

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

**In-app purchases (8)**

| Purchase | Price | Billing |
| --- | --- | --- |
| +30 User Tokens | $0.29 | one-time |
| +1 Convenience Token / 6h, max. +2 | $0.59 | one-time |
| +2 Convenience Tokens / 6h, max. +4 | $0.99 | one-time |
| +150 User Tokens | $0.99 | one-time |
| +300 User Tokens | $1.49 | one-time |
| +4 Convenience Tokens / 6h, max. +8 | $1.59 | one-time |
| Lifetime Access | $1.99 | one-time |
| Remove Ads | $1.99 | one-time |


### ReadBay

[App page](https://appshunter.io/ios/app/readbay-book-summaries/id6499073338)

Access concise summaries and audio versions of bestselling books in under 15 minutes. Master key insights from business, self-help, and personal development titles for faster learning and habit building.

**Highlights:** 15-minute book summaries, Audiobook summaries, Offline reading, Progress tracking, Habit building challenges, Bookmark favorite notes

**Features:** macOS Compatibility

**In-app purchases (4)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Monthly Pro Membership | $4.99 | per month |
| Pro Annual Membership | $19.99 | per year |
| Yearly Pro Membership | $24.99 | per year |
| Lifetime Membership | $39.99 | one-time |

**What reviewers like**

- 🚀 Informative and easy to follow
- 👍 Smooth listening experience
- 👍 Broad library of titles
- 👍 Allows reading or listening
- 👍 User-friendly interface

**What reviewers complain about**

- 🐛 Usability issues when multitasking
- 🐛 Audiobook restarts from beginning
- 🔒 Lack of transparency (broken links, no contact info)
- 👎 Limited book recommendations
- 👎 Needs more book options and larger selection

**Reported bugs**

- Purchased lifetime subscription not accessible on new device
- Identical summaries for different books

**Requested features**

- Support for French books
- Ability to share summaries to Kindle
- More language options (e.g., Chinese)


## Frequently asked questions

### Is Combinatorics Calculator free?

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

### Is ReadBay free?

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

### Do Combinatorics Calculator or ReadBay have ads?

Neither Combinatorics Calculator nor ReadBay shows ads.

### Which is updated more often, Combinatorics Calculator or ReadBay?

Combinatorics Calculator ships an update every 3 weeks, and ReadBay every 10 days. Most recently, Combinatorics Calculator was updated on October 24, 2026 and ReadBay on October 23, 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.*