# Fast Slow vs CalCrunch

The clearest difference is update cadence: Fast Slow at every 2 weeks against CalCrunch's monthly. Fast Slow also leads on iOS requirement (18.0 vs 26.0). On price, ads, in-app purchases and device support there is nothing between them.

Both are free to download. Fast Slow sells 4 in-app purchases, starting at $1.99 per 7 days and CalCrunch sells 1 one-off in-app purchase. Whichever you choose, the download price is not the number that matters.

Fast Slow ships an update every 2 weeks, CalCrunch monthly. The most recent releases landed on October 24, 2026 and October 4, 2026 respectively.

## The numbers

| Metric | Fast Slow | CalCrunch |
| --- | --- | --- |
| Price | Free | Free |
| Rating | **[5.0 (39 ratings)](https://appshunter.io/ios/app/fast-slow-fasting-tracker/id6749188352/reviews)** | — |
| Number of ratings | **39** | — |
| Positive reviews | 100.0% of reviews | — |
| In-app purchases | Yes | Yes |
| Ads | No | No |
| Update frequency | **Every 2 weeks** | Monthly |
| Monetization | Free | — |
| Size | 23 MB | 15 MB |
| Requires iOS | **18.0** | 26.0 |
| Devices | iPhone | **iPhone, iPad** |
| Age rating | 4+ | 4+ |
| Developer | [Zan Cerne](https://appshunter.io/developer/1747198932) | [Banana Logic, LLC](https://appshunter.io/developer/1856746700) |

## What reviewers say

### Fast Slow

[App page](https://appshunter.io/ios/app/fast-slow-fasting-tracker/id6749188352)

Understand your body's metabolic changes during fasting with a visual timeline. This free app guides you through different fasting zones, from digestion to deep ketosis, and offers customizable schedules and smart notifications. It provides stats, streaks, and widgets for easy progress tracking.

**Highlights:** Fasting timer with visual timeline, 6 customizable fasting schedules, 5 distinct fasting zones explained, Smart notifications for fasting windows, Stats, streaks, and trends tracking, Home and Lock Screen widgets, Siri Shortcuts integration

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

**In-app purchases (4)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Legacy | $1.99 | per 7 days |
| Legacy - Yearly | $12.99 | per year |
| Buy Me a Coffee | $2.99 | one-time |
| You're Amazing | $9.99 | one-time |


### CalCrunch

[App page](https://appshunter.io/ios/app/calcrunch/id6755857556)

**Features:** macOS Compatibility, Family Sharing

**In-app purchases (1)**

| Purchase | Price | Billing |
| --- | --- | --- |
| CalCrunch+ | $9.99 | one-time |


## Frequently asked questions

### Is Fast Slow free?

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

### Is CalCrunch free?

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

### Do Fast Slow or CalCrunch have ads?

Neither Fast Slow nor CalCrunch shows ads.

### Which is updated more often, Fast Slow or CalCrunch?

Fast Slow ships an update every 2 weeks, and CalCrunch monthly. Most recently, Fast Slow was updated on October 24, 2026 and CalCrunch on October 4, 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.*