# Prefix App vs Unit Converter Engineering Pro

The clearest difference is in-app purchases: Prefix App at none against Unit Converter Engineering Pro's 2. Prefix App also leads on iOS requirement (7.0 vs 13.0). On price, update cadence, ads and device support there is nothing between them.

Both are free to download. Unit Converter Engineering Pro sells 2 in-app purchases, starting at $5.99 per 7 days. Prefix App asks for nothing beyond the download.

Prefix App ships an update fortnightly, Unit Converter Engineering Pro weekly. The most recent releases landed on October 9, 2026 and October 2, 2026 respectively.

## The numbers

| Metric | Prefix App | Unit Converter Engineering Pro |
| --- | --- | --- |
| Price | Free | Free |
| Rating | — | **[5.0 (1 ratings)](https://appshunter.io/ios/app/unit-converter-engineering-pro/id6757166485/reviews)** |
| Number of ratings | — | **1** |
| Positive reviews | 48.3% of reviews | — |
| In-app purchases | **No** | Yes |
| Ads | No | No |
| Update frequency | Fortnightly | **Weekly** |
| Monetization | **Free** | Free with in-app purchases |
| Size | 21 MB | 77 MB |
| Requires iOS | **7.0** | 13.0 |
| Devices | iPhone, iPod | **iPhone, iPad, iPod** |
| Age rating | 4+ | 4+ |
| Developer | [Alain Lima](https://appshunter.io/developer/789421888) | [Kaiguri Tech](https://appshunter.io/developer/1864995084) |

## What reviewers say

### Prefix App

[App page](https://appshunter.io/ios/app/prefix-app/id813922085)

Easily add a prefix to phone numbers before dialing without altering your contacts. Ideal for managing business phone lines or specific calling requirements directly from your address book or keypad.

**Highlights:** Full address book access, Customizable contacts, Recent calls list, Customizable prefix and suffix, Direct dialing via keypad, Intuitive interface

**Features:** macOS Compatibility

**In-app purchases:** none


### Unit Converter Engineering Pro

[App page](https://appshunter.io/ios/app/unit-converter-engineering-pro/id6757166485)

This app provides precise unit conversions for engineers, scientists, and students. It supports over 100 units across 35 categories, including scientific notation and 9-digit decimal precision. The tool works offline and adheres to SI, NIST, and ISO standards.

**Highlights:** Over 100 units in 35+ categories, Scientific notation support, 9-digit decimal precision, SI, NIST, ISO compliant, Offline functionality, Specialized units included

**Features:** macOS Compatibility

**In-app purchases (2)**

| Purchase | Price | Billing |
| --- | --- | --- |
| 3-Day Trial | $5.99 | per 7 days |
| Yearly Plan | $19.99 | per year |


## Frequently asked questions

### Is Prefix App free?

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

### Is Unit Converter Engineering Pro free?

Unit Converter Engineering Pro is free to download, with in-app purchases available.

### Do Prefix App or Unit Converter Engineering Pro have ads?

Neither Prefix App nor Unit Converter Engineering Pro shows ads.

### Which is updated more often, Prefix App or Unit Converter Engineering Pro?

Prefix App ships an update fortnightly, and Unit Converter Engineering Pro weekly. Most recently, Prefix App was updated on October 9, 2026 and Unit Converter Engineering Pro on October 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.*