# Mechanical Engineer vs D

The clearest difference is in-app purchases: D at none against Mechanical Engineer's 3. D also leads on iOS requirement (13.0 vs 17.6). On price, update cadence, ads and device support there is nothing between them.

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

Both ship on a similar rhythm, roughly every 2 months. The most recent releases landed on August 13, 2026 and September 18, 2026 respectively.

## The numbers

| Metric | Mechanical Engineer | D |
| --- | --- | --- |
| Price | Free | Free |
| Rating | **[4.4 (8 ratings)](https://appshunter.io/ios/app/mechanical-engineer/id327055140/reviews)** | — |
| Number of ratings | **8** | — |
| Positive reviews | 30.8% of reviews | — |
| In-app purchases | Yes | **No** |
| Ads | No | No |
| Update frequency | Every 2 months | Every 2 months |
| Monetization | Free with in-app purchases | — |
| Size | 5 MB | 15 MB |
| Requires iOS | 17.6 | **13.0** |
| Devices | iPhone, iPad | **iPhone, iPad, iPod** |
| Age rating | 4+ | 4+ |
| Developer | [Historycentral.com](https://appshunter.io/developer/1744330560) | [Winkong Marine Engineering Co.,Ltd.](https://appshunter.io/developer/1602619555) |

## 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 |


### D

[App page](https://appshunter.io/ios/app/d-vesselkeeper/id6677012335)

**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 D free?

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

### Do Mechanical Engineer or D have ads?

Neither Mechanical Engineer nor D shows ads.

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

Mechanical Engineer ships an update every 2 months, and D every 2 months. Most recently, Mechanical Engineer was updated on August 13, 2026 and D on September 18, 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.*