# SI Prefix Converter vs UnitSnap

The clearest difference is in-app purchases: SI Prefix Converter at none against UnitSnap's 1. SI Prefix Converter also leads on ads (none vs shown) and device support (3 vs 1). UnitSnap's advantage is update cadence (every 4 months vs every 9 months). On price there is nothing between them.

Both are free to download. UnitSnap sells 1 one-off in-app purchase. SI Prefix Converter asks for nothing beyond the download.

SI Prefix Converter ships an update every 9 months, UnitSnap every 4 months. The most recent releases landed on October 26, 2026 and October 14, 2026 respectively.

## The numbers

| Metric | SI Prefix Converter | UnitSnap |
| --- | --- | --- |
| Price | Free | Free |
| In-app purchases | **No** | Yes |
| Ads | **No** | Yes |
| Update frequency | Every 9 months | **Every 4 months** |
| Size | 23 MB | 4 MB |
| Requires iOS | **8.0** | 17.6 |
| Devices | **iPhone, iPad, iPod** | iPhone |
| Age rating | 4+ | 4+ |
| Developer | [Yuki Takeda](https://appshunter.io/developer/1021096508) | [Chia-Chun Hsieh](https://appshunter.io/developer/908221958) |

## What reviewers say

### SI Prefix Converter

[App page](https://appshunter.io/ios/app/si-prefix-converter/id1047118885)

**Features:** Vision Pro support

**In-app purchases:** none


### UnitSnap

[App page](https://appshunter.io/ios/app/unitsnap/id6742785813)

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

**In-app purchases (1)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Remove Ads | $0.99 | one-time |


## Frequently asked questions

### Is SI Prefix Converter free?

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

### Is UnitSnap free?

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

### Do SI Prefix Converter or UnitSnap have ads?

UnitSnap shows ads; SI Prefix Converter does not.

### Which is updated more often, SI Prefix Converter or UnitSnap?

SI Prefix Converter ships an update every 9 months, and UnitSnap every 4 months. Most recently, SI Prefix Converter was updated on October 26, 2026 and UnitSnap on October 14, 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.*