# Calibre Biometrics vs O2CO2

Calibre Biometrics and O2CO2 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. Calibre Biometrics sells 1 in-app purchase, starting at $7.99 per month and O2CO2 sells 2 in-app purchases, starting at $3.99 per year. Whichever you choose, the download price is not the number that matters.

Calibre Biometrics ships an update every 4 weeks, O2CO2 every 3 weeks. The most recent releases landed on November 4, 2026 and October 31, 2026 respectively.

## The numbers

| Metric | Calibre Biometrics | O2CO2 |
| --- | --- | --- |
| Price | Free | Free |
| Rating | **[4.5 (2 ratings)](https://appshunter.io/ios/app/calibre-biometrics/id6743721886/reviews)** | — |
| Number of ratings | **2** | — |
| Positive reviews | 50.0% of reviews | — |
| In-app purchases | Yes | Yes |
| Ads | No | No |
| Update frequency | Every 4 weeks | **Every 3 weeks** |
| Monetization | Free | — |
| Size | 116 MB | 353 MB |
| Requires iOS | 15.4 | **15.1** |
| Devices | **iPhone, iPad, iPod** | iPhone, iPod |
| Age rating | 4+ | 4+ |
| Developer | [BreathTaking Tech LLC](https://appshunter.io/developer/1609706657) | [ELIOTT ROMAIN-SAVARD](https://appshunter.io/developer/6813168270) |

## What reviewers say

### Calibre Biometrics

[App page](https://appshunter.io/ios/app/calibre-biometrics/id6743721886)

This app pairs with a wearable device to track and analyze key metabolic and performance metrics like VO2 Max and resting metabolic rate. It provides detailed insights into your body's energy expenditure and fat burning zones. Designed for informational and educational use, it complements professional health guidance.

**Highlights:** View biometric data, Record metabolic information, Analyze VO2 Max, Monitor Resting Metabolic Rate, Track FatMax and Calories, Companion to wearable tracker

**In-app purchases (1)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Calibre Premium | $7.99 | per month |


### O2CO2

[App page](https://appshunter.io/ios/app/o2co2/id6813168268)

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

**In-app purchases (2)**

| Purchase | Price | Billing |
| --- | --- | --- |
| O2CO2 Premium Annual | $3.99 | per year |
| O2CO2 Premium Lifetime | $14.99 | one-time |


## Frequently asked questions

### Is Calibre Biometrics free?

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

### Is O2CO2 free?

O2CO2 is free to download, with in-app purchases available.

### Do Calibre Biometrics or O2CO2 have ads?

Neither Calibre Biometrics nor O2CO2 shows ads.

### Which is updated more often, Calibre Biometrics or O2CO2?

Calibre Biometrics ships an update every 4 weeks, and O2CO2 every 3 weeks. Most recently, Calibre Biometrics was updated on November 4, 2026 and O2CO2 on October 31, 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.*