# 555 Calc vs Currency Professional

The clearest difference is in-app purchases: 555 Calc at none against Currency Professional's 1. 555 Calc also leads on iOS requirement (11.0 vs 26.0). Currency Professional's advantage is ads (none vs shown) and update cadence (every 5 months vs every 20 months). On price and device support there is nothing between them.

Both are free to download. Currency Professional sells 1 one-off in-app purchase. 555 Calc asks for nothing beyond the download.

555 Calc ships an update every 20 months, Currency Professional every 5 months. The most recent releases landed on October 28, 2026 and October 25, 2026 respectively.

## The numbers

| Metric | 555 Calc | Currency Professional |
| --- | --- | --- |
| Price | Free | Free |
| Rating | **[4.0 (3 ratings)](https://appshunter.io/ios/app/555-calc/id868058244/reviews)** | — |
| Number of ratings | **3** | — |
| Positive reviews | 50.0% of reviews | — |
| In-app purchases | **No** | Yes |
| Ads | Yes | **No** |
| Update frequency | Every 20 months | **Every 5 months** |
| Monetization | Ad-supported | — |
| Size | 18 MB | 21 MB |
| Requires iOS | **11.0** | 26.0 |
| Devices | **iPhone, iPad, iPod** | iPhone, iPad |
| Age rating | 4+ | 4+ |
| Developer | [Jibiki Works](https://appshunter.io/developer/556845808) | [Gerhard Lentschik](https://appshunter.io/developer/629988041) |

## What reviewers say

### 555 Calc

[App page](https://appshunter.io/ios/app/555-calc/id868058244)

This utility app helps engineers and hobbyists calculate resistor values for circuits using the Timer IC 555. Simply input frequency, duty ratio, and capacitor values to get the required resistor outputs.

**Highlights:** Calculate resistor values, Input frequency, Input duty ratio, Input capacitor value, Timer IC 555 circuit design

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

**In-app purchases:** none


### Currency Professional

[App page](https://appshunter.io/ios/app/currency-professional/id1493772243)

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

**In-app purchases (1)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Remove Advertising | $1.99 | one-time |


## Frequently asked questions

### Is 555 Calc free?

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

### Is Currency Professional free?

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

### Do 555 Calc or Currency Professional have ads?

555 Calc shows ads; Currency Professional does not.

### Which is updated more often, 555 Calc or Currency Professional?

555 Calc ships an update every 20 months, and Currency Professional every 5 months. Most recently, 555 Calc was updated on October 28, 2026 and Currency Professional on October 25, 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.*