# Calibrate vs Prep Clock

The clearest difference is update cadence: Prep Clock at every 4 days against Calibrate's fortnightly. On price, ads, in-app purchases and device support there is nothing between them.

Both are free to download. Calibrate sells 1 one-off in-app purchase and Prep Clock sells 2 in-app purchases, starting at $2.99 per month. Whichever you choose, the download price is not the number that matters.

Calibrate ships an update fortnightly, Prep Clock every 4 days. The most recent releases landed on September 10, 2026 and September 9, 2026 respectively.

## The numbers

| Metric | Calibrate | Prep Clock |
| --- | --- | --- |
| Price | Free | Free |
| In-app purchases | Yes | Yes |
| Ads | No | No |
| Update frequency | Fortnightly | **Every 4 days** |
| Size | 4 MB | 16 MB |
| Requires iOS | **17.6** | 18.0 |
| Devices | iPhone, iPad | iPhone, iPad |
| Age rating | 4+ | 4+ |
| Developer | [Warren Peters](https://appshunter.io/developer/1591974619) | [Ryan Tinklepaugh](https://appshunter.io/developer/1883444651) |

## What reviewers say

### Calibrate

[App page](https://appshunter.io/ios/app/calibrate-time-block-planner/id6758213974)

**Features:** macOS Compatibility

**In-app purchases (1)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Calibrate Pro — Lifetime | $9.99 | one-time |


### Prep Clock

[App page](https://appshunter.io/ios/app/prep-clock-backward-timer/id6760279596)

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

**In-app purchases (2)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Pro Monthly | $2.99 | per month |
| Pro Annual | $19.99 | per year |


## Frequently asked questions

### Is Calibrate free?

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

### Is Prep Clock free?

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

### Do Calibrate or Prep Clock have ads?

Neither Calibrate nor Prep Clock shows ads.

### Which is updated more often, Calibrate or Prep Clock?

Calibrate ships an update fortnightly, and Prep Clock every 4 days. Most recently, Calibrate was updated on September 10, 2026 and Prep Clock on September 9, 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.*