# O vs Fluid Mechanics Calc

The clearest difference is device support: Fluid Mechanics Calc at 3 against O's 1. Fluid Mechanics Calc also leads on ratings volume (3 vs 1). On price, rating, update cadence and ads there is nothing between them.

Both are free to download. Neither carries in-app purchases, so what you see is what you pay.

On the App Store both sit at effectively the same score — 5.0 for O against 5.0 for Fluid Mechanics Calc. Both are backed by a comparable volume of ratings — 1 and 3 respectively.

O ships an update every 11 months, Fluid Mechanics Calc every 22 months. Both last shipped on November 2, 2026.

## The numbers

| Metric | O | Fluid Mechanics Calc |
| --- | --- | --- |
| Price | Free | Free |
| Rating | [5.0 (1 ratings)](https://appshunter.io/ios/app/o-ring-master/id1072051820/reviews) | [5.0 (3 ratings)](https://appshunter.io/ios/app/fluid-mechanics-calc/id1404879538/reviews) |
| Number of ratings | 1 | **3** |
| Positive reviews | 100.0% of reviews | — |
| In-app purchases | No | No |
| Ads | No | No |
| Update frequency | **Every 11 months** | Every 22 months |
| Monetization | Free | Free |
| Size | 47 MB | 108 MB |
| Requires iOS | 16.0 | **15.6** |
| Devices | iPhone | **iPhone, iPad, iPod** |
| Age rating | 4+ | 4+ |
| Developer | [GE MAO RUBBER INDUSTRIAL CO., LTD.](https://appshunter.io/developer/1078558543) | [Trelleborg Sealing Solutions](https://appshunter.io/developer/396863758) |

## What reviewers say

### O

[App page](https://appshunter.io/ios/app/o-ring-master/id1072051820)

This app provides a comprehensive offline tool for selecting standard rubber seal sizes, including O-Rings, X-Rings, and Back-Up Rings. It offers dimension searches, housing calculations for various sealing applications, and supports multiple international standards in both metric and imperial units.

**Highlights:** Offline standard rubber seal size selection, Search for O-Ring, X-Ring, and Back-Up Ring sizes, O-Ring housing calculations for sealing applications, Supports multiple international standards (AS568, METRIC, JIS, etc.), Metric and Imperial unit support, Substitutable O-Ring size suggestions

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

**In-app purchases:** none


### Fluid Mechanics Calc

[App page](https://appshunter.io/ios/app/fluid-mechanics-calc/id1404879538)

This utility app provides a comprehensive calculator for fluid mechanics, civil, and structural engineering parameters. It offers over 130 formulas and 360 calculation methods, supporting seamless unit system switching for analysis, design, and operation of fluid-related systems.

**Highlights:** 130+ fluid mechanics formulas, 360+ calculation methods, Unit system conversion (metric/US), Favorite formula marking, High mathematical precision, Seamless unit switching

**Features:** macOS Compatibility

**In-app purchases:** none


## Frequently asked questions

### Is O free?

O is free to download, with no in-app purchases.

### Is Fluid Mechanics Calc free?

Fluid Mechanics Calc is free to download, with no in-app purchases.

### Which has better reviews, O or Fluid Mechanics Calc?

O and Fluid Mechanics Calc are both rated 5.0 out of 5 on the App Store, from 1 and 3 ratings respectively.

### Do O or Fluid Mechanics Calc have ads?

Neither O nor Fluid Mechanics Calc shows ads.

### Which is updated more often, O or Fluid Mechanics Calc?

O ships an update every 11 months, and Fluid Mechanics Calc every 22 months. Most recently, O was updated on November 2, 2026 and Fluid Mechanics Calc on November 2, 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.*