# Mechanical Engineer vs O

The clearest difference is review sentiment: O at 83% against Mechanical Engineer's 31%. O also leads on in-app purchases (none vs 3) and iOS requirement (12.1 vs 17.6). Mechanical Engineer's advantage is rating (4.4 vs 3.8). On price, ratings volume, update cadence and ads there is nothing between them.

Both are free to download. Mechanical Engineer sells 3 in-app purchases, starting at $0.99 per month. O asks for nothing beyond the download.

Mechanical Engineer holds the better App Store score, 4.4 against 3.8. Both are backed by a comparable volume of ratings — 8 and 5 respectively. Written reviews complicate that: 31% of Mechanical Engineer's written reviews are positive against 83% of O's, so the app with the better star average is not the one people write more warmly about.

Mechanical Engineer ships an update every 2 months, O every 3 months. The most recent releases landed on August 13, 2026 and June 4, 2026 respectively.

## The numbers

| Metric | Mechanical Engineer | O |
| --- | --- | --- |
| Price | Free | Free |
| Rating | **[4.4 (8 ratings)](https://appshunter.io/ios/app/mechanical-engineer/id327055140/reviews)** | [3.8 (5 ratings)](https://appshunter.io/ios/app/o-ring/id485346224/reviews) |
| Number of ratings | **8** | 5 |
| Positive reviews | 30.8% of reviews | **83.3% of reviews** |
| In-app purchases | Yes | **No** |
| Ads | No | No |
| Update frequency | **Every 2 months** | Every 3 months |
| Monetization | Free with in-app purchases | **Free** |
| Size | 5 MB | 26 MB |
| Requires iOS | 17.6 | **12.1** |
| Devices | iPhone, iPad | **iPhone, iPad, iPod** |
| Age rating | 4+ | 12+ |
| Developer | [Historycentral.com](https://appshunter.io/developer/1744330560) | [Trelleborg Sealing Solutions](https://appshunter.io/developer/396863758) |

## What reviewers say

### Mechanical Engineer

[App page](https://appshunter.io/ios/app/mechanical-engineer/id327055140)

This app provides over 300 essential mechanical engineering formulas across various domains. It allows users to calculate, save, compare, and share results, aiding in project optimization and decision-making. Users can access a limited number of calculations for free, with a subscription unlocking full functionality.

**Highlights:** Over 300 mechanical engineering formulas, Covers diverse engineering domains, Save and compare formula results, Share calculation outcomes, Intuitive and practical interface, Regular updates based on user input

**Features:** macOS Compatibility

**In-app purchases (3)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Monthly Subscription | $0.99 | per month |
| Pro Quarterly | $0.99 | per 3 months |
| Pro Yearly | $2.99 | per year |


### O

[App page](https://appshunter.io/ios/app/o-ring/id485346224)

This app helps users calculate O-Ring dimensions and find compatible materials for their applications. It provides recommendations based on ISO standards and supports both metric and inch measurements.

**Highlights:** O-Ring housing calculation, O-Ring size recommendations by ISO standard, Quick search by national/international standards, O-Ring tolerance calculation, Metric and inch unit switching, Chemical compatibility check, Integration of Trelleborg Sealing Solutions Videos

**Features:** macOS Compatibility

**In-app purchases:** none


## Frequently asked questions

### Is Mechanical Engineer free?

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

### Is O free?

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

### Which has better reviews, Mechanical Engineer or O?

Mechanical Engineer is rated higher. Mechanical Engineer averages 4.4 out of 5 from 8 ratings, while O averages 3.8 from 5 ratings.

### Do Mechanical Engineer or O have ads?

Neither Mechanical Engineer nor O shows ads.

### Which is updated more often, Mechanical Engineer or O?

Mechanical Engineer ships an update every 2 months, and O every 3 months. Most recently, Mechanical Engineer was updated on August 13, 2026 and O on June 4, 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.*