# O2 Duration vs Unit Converter For Medics

The clearest difference is price: Unit Converter For Medics at Free against O2 Duration's $2.99. Unit Converter For Medics also leads on update cadence (every 7 months vs every 15 months). O2 Duration's advantage is iOS requirement (7.0 vs 12.1). On ads, in-app purchases and device support there is nothing between them.

Unit Converter For Medics is free to download; O2 Duration costs $2.99 up front. Neither carries in-app purchases, so what you see is what you pay.

O2 Duration ships an update every 15 months, Unit Converter For Medics every 7 months. The most recent releases landed on October 15, 2026 and October 25, 2026 respectively.

## The numbers

| Metric | O2 Duration | Unit Converter For Medics |
| --- | --- | --- |
| Price | $2.99 | **Free** |
| Rating | **[1.0 (1 ratings)](https://appshunter.io/ios/app/o2-duration/id556420187/reviews)** | — |
| Number of ratings | **1** | — |
| Positive reviews | 0.0% of reviews | — |
| In-app purchases | No | No |
| Ads | No | No |
| Update frequency | Every 15 months | **Every 7 months** |
| Monetization | Paid | — |
| Size | 1 MB | 14 MB |
| Requires iOS | **7.0** | 12.1 |
| Devices | iPhone, iPod | **iPhone, iPad, iPod** |
| Age rating | 4+ | 4+ |
| Developer | [Advanced Aviation LLC](https://appshunter.io/developer/540245667) | [Krzysztof Gwiazda](https://appshunter.io/developer/1546740383) |

## What reviewers say

### O2 Duration

[App page](https://appshunter.io/ios/app/o2-duration/id556420187)

Calculate the approximate remaining oxygen in portable cylinders. Select your tank size, input current pressure and desired flow rate to see duration in minutes. Features a timer with alerts for low pressure.

**Highlights:** Oxygen cylinder duration calculation, Supports multiple cylinder sizes (A, B, D, E, G, H, K, M), Input current tank pressure, Input desired flow rate, Displays duration in minutes, Running timer with remaining time, Low pressure alerts (500lbs and 0lbs)

**Features:** macOS Compatibility

**In-app purchases:** none


### Unit Converter For Medics

[App page](https://appshunter.io/ios/app/unit-converter-for-medics/id1634088201)

**Features:** macOS Compatibility

**In-app purchases:** none


## Frequently asked questions

### Is O2 Duration free?

O2 Duration costs $2.99, with no in-app purchases.

### Is Unit Converter For Medics free?

Unit Converter For Medics is free to download, with no in-app purchases.

### Do O2 Duration or Unit Converter For Medics have ads?

Neither O2 Duration nor Unit Converter For Medics shows ads.

### Which is updated more often, O2 Duration or Unit Converter For Medics?

O2 Duration ships an update every 15 months, and Unit Converter For Medics every 7 months. Most recently, O2 Duration was updated on October 15, 2026 and Unit Converter For Medics on October 25, 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.*