# O2gO2 vs On the hour

The clearest difference is rating: On the hour at 4.0 against O2gO2's 3.0. On the hour also leads on in-app purchases (none vs 1) and update cadence (weekly vs every 28 months). O2gO2's advantage is iOS requirement (12.0 vs 15.1). On price, ratings volume, ads and device support there is nothing between them.

Both are free to download. O2gO2 sells 1 in-app purchase, starting at $2.99 per year. On the hour asks for nothing beyond the download.

On the hour holds the better App Store score, 4.0 against 3.0. Both are backed by a comparable volume of ratings — 2 and 2 respectively.

O2gO2 ships an update every 28 months, On the hour weekly. The most recent releases landed on October 19, 2026 and October 24, 2026 respectively.

## The numbers

| Metric | O2gO2 | On the hour |
| --- | --- | --- |
| Price | Free | Free |
| Rating | [3.0 (2 ratings)](https://appshunter.io/ios/app/o2go2/id895990670/reviews) | **[4.0 (2 ratings)](https://appshunter.io/ios/app/on-the-hour/id6753136689/reviews)** |
| Number of ratings | 2 | 2 |
| In-app purchases | Yes | **No** |
| Ads | No | No |
| Update frequency | Every 28 months | **Weekly** |
| Monetization | Free with in-app purchases | **Free** |
| Size | 2 MB | 28 MB |
| Requires iOS | **12.0** | 15.1 |
| Devices | **iPhone, iPad, iPod** | iPhone, iPod |
| Age rating | 4+ | 4+ |
| Developer | [Aeronautical Data Systems Inc.](https://appshunter.io/developer/552304929) | [田丰 何](https://appshunter.io/developer/1674464316) |

## What reviewers say

### O2gO2

[App page](https://appshunter.io/ios/app/o2go2/id895990670)

This utility app converts oxygen cylinder pressure into remaining time, helping users manage their compressed gas resources. It provides visual indicators and calculates duration based on tank size, current pressure, and flow rate.

**Highlights:** Converts PSI to time remaining, Calculates duration based on tank size, pressure, and flow rate, Visual multicolored strip indicates oxygen level, Yellow and red indicators for low oxygen, Automatic reset for pressure input, Assumes consistent tank size

**Features:** macOS Compatibility

**In-app purchases (1)**

| Purchase | Price | Billing |
| --- | --- | --- |
| O2 Go2 Yearly Subscription | $2.99 | per year |


### On the hour

[App page](https://appshunter.io/ios/app/on-the-hour/id6753136689)

This utility app provides a single, focused function: a chime that sounds precisely on the hour. It's designed for users who need a simple, reliable auditory reminder of passing time.

**Highlights:** Hourly chime notification, Simple, single-function design, Reliable timekeeping alert

**Features:** macOS Compatibility

**In-app purchases:** none


## Frequently asked questions

### Is O2gO2 free?

O2gO2 is free to download, with in-app purchases available.

### Is On the hour free?

On the hour is free to download, with no in-app purchases.

### Which has better reviews, O2gO2 or On the hour?

On the hour is rated higher. O2gO2 averages 3.0 out of 5 from 2 ratings, while On the hour averages 4.0 from 2 ratings.

### Do O2gO2 or On the hour have ads?

Neither O2gO2 nor On the hour shows ads.

### Which is updated more often, O2gO2 or On the hour?

O2gO2 ships an update every 28 months, and On the hour weekly. Most recently, O2gO2 was updated on October 19, 2026 and On the hour on October 24, 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.*