# O vs Hydraulic Calculator Engineer

The clearest difference is rating: O at 5.0 against Hydraulic Calculator Engineer's 4.3. Hydraulic Calculator Engineer's advantage is ratings volume (9 vs 1) and device support (3 vs 1). On price, update cadence, ads and in-app purchases there is nothing between them.

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

O holds the better App Store score, 5.0 against 4.3. That said, the two scores are not equally well evidenced: Hydraulic Calculator Engineer has 9 ratings behind it against 1, so its average is the more settled of the two.

O ships an update every 11 months, Hydraulic Calculator Engineer every 22 months. The most recent releases landed on September 22, 2026 and September 10, 2026 respectively.

## The numbers

| Metric | O | Hydraulic Calculator Engineer |
| --- | --- | --- |
| Price | Free | Free |
| Rating | **[5.0 (1 ratings)](https://appshunter.io/ios/app/o-ring-master/id1072051820/reviews)** | [4.3 (9 ratings)](https://appshunter.io/ios/app/hydraulic-calculator-engineer/id1664790770/reviews) |
| Number of ratings | 1 | **9** |
| Positive reviews | — | 0.0% of reviews |
| In-app purchases | No | No |
| Ads | No | No |
| Update frequency | **Every 11 months** | Every 22 months |
| Monetization | Free | Free |
| Size | 47 MB | 21 MB |
| Requires iOS | 16.0 | **15.0** |
| Devices | iPhone | **iPhone, iPad, iPod** |
| Age rating | 4+ | 4+ |
| Developer | [GE MAO RUBBER INDUSTRIAL CO., LTD.](https://appshunter.io/developer/1078558543) | [Arsosa Network Inc.](https://appshunter.io/developer/1209042440) |

## 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


### Hydraulic Calculator Engineer

[App page](https://appshunter.io/ios/app/hydraulic-calculator-engineer/id1664790770)

This app offers a suite of hydraulic calculations for technicians and engineers. It simplifies complex hydraulics by automatically computing results based on user-entered values, eliminating the need for manual formula application.

**Highlights:** Cylinder Calculation, Power Calculation, Pressure Difference, Piston Diameter, Speed Calculation, Lifting Time, Volume Flow

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

**In-app purchases:** none


## Frequently asked questions

### Is O free?

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

### Is Hydraulic Calculator Engineer free?

Hydraulic Calculator Engineer is free to download, with no in-app purchases.

### Which has better reviews, O or Hydraulic Calculator Engineer?

O is rated higher. O averages 5.0 out of 5 from 1 ratings, while Hydraulic Calculator Engineer averages 4.3 from 9 ratings.

### Do O or Hydraulic Calculator Engineer have ads?

Neither O nor Hydraulic Calculator Engineer shows ads.

### Which is updated more often, O or Hydraulic Calculator Engineer?

O ships an update every 11 months, and Hydraulic Calculator Engineer every 22 months. Most recently, O was updated on September 22, 2026 and Hydraulic Calculator Engineer on September 10, 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.*