# Engineering Formulas vs Architect Lexicon

The clearest difference is in-app purchases: Architect Lexicon at none against Engineering Formulas's 3. Architect Lexicon also leads on update cadence (fortnightly vs every 2 months). On price, ads, device support and iOS requirement there is nothing between them.

Both are free to download. Engineering Formulas sells 3 in-app purchases, starting at $4.99 per 7 days. Architect Lexicon asks for nothing beyond the download.

Engineering Formulas ships an update every 2 months, Architect Lexicon fortnightly. The most recent releases landed on October 20, 2026 and October 11, 2026 respectively.

## The numbers

| Metric | Engineering Formulas | Architect Lexicon |
| --- | --- | --- |
| Price | Free | Free |
| In-app purchases | Yes | **No** |
| Ads | No | No |
| Update frequency | Every 2 months | **Fortnightly** |
| Size | 45 MB | 41 MB |
| Requires iOS | 15.1 | **15.0** |
| Devices | iPhone, iPad, iPod | iPhone, iPad, iPod |
| Age rating | 12+ | 4+ |
| Developer | [Mobin Akhter](https://appshunter.io/developer/1812505286) | [Sudarson Raja](https://appshunter.io/developer/1896603613) |

## What reviewers say

### Engineering Formulas

[App page](https://appshunter.io/ios/app/engineering-formulas-engiref/id6758258119)

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

**In-app purchases (3)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Weekly Premium | $4.99 | per 7 days |
| Yearly Premium | $29.99 | per year |
| Lifetime Access | $54.99 | one-time |


### Architect Lexicon

[App page](https://appshunter.io/ios/app/architect-lexicon/id6768775843)

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

**In-app purchases:** none


## Frequently asked questions

### Is Engineering Formulas free?

Engineering Formulas is free to download, with in-app purchases available.

### Is Architect Lexicon free?

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

### Do Engineering Formulas or Architect Lexicon have ads?

Neither Engineering Formulas nor Architect Lexicon shows ads.

### Which is updated more often, Engineering Formulas or Architect Lexicon?

Engineering Formulas ships an update every 2 months, and Architect Lexicon fortnightly. Most recently, Engineering Formulas was updated on October 20, 2026 and Architect Lexicon on October 11, 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.*