# Timer 555 Calculator vs Units2Units

The clearest difference is update cadence: Units2Units at every 6 days against Timer 555 Calculator's every 3 months. Timer 555 Calculator's advantage is iOS requirement (13.2 vs 16.0). On price, ads, in-app purchases and device support there is nothing between them.

Both are free to download. Timer 555 Calculator sells 1 one-off in-app purchase and Units2Units sells 1 one-off in-app purchase. Whichever you choose, the download price is not the number that matters.

Timer 555 Calculator ships an update every 3 months, Units2Units every 6 days. The most recent releases landed on October 5, 2026 and October 4, 2026 respectively.

## The numbers

| Metric | Timer 555 Calculator | Units2Units |
| --- | --- | --- |
| Price | Free | Free |
| Rating | **[3.9 (8 ratings)](https://appshunter.io/ios/app/timer-555-calculator/id834044557/reviews)** | — |
| Number of ratings | **8** | — |
| Positive reviews | 100.0% of reviews | — |
| In-app purchases | Yes | Yes |
| Ads | No | No |
| Update frequency | Every 3 months | **Every 6 days** |
| Monetization | Free with in-app purchases | — |
| Size | 3 MB | 44 MB |
| Requires iOS | **13.2** | 16.0 |
| Devices | **iPhone, iPad, iPod** | iPhone, iPad |
| Age rating | 4+ | 4+ |
| Developer | [Siu Yuen Ho](https://appshunter.io/developer/814088527) | [GnitoApp.com](https://appshunter.io/developer/1804710946) |

## What reviewers say

### Timer 555 Calculator

[App page](https://appshunter.io/ios/app/timer-555-calculator/id834044557)

Calculate monostable and astable circuits for electronics projects. Determine pulse width and frequency, find component combinations, and save/upload data. Supports multiple languages.

**Highlights:** Monostable circuit pulse width calculation, Astable circuit frequency calculation, Component combination finder, Save component values to CSV, Upload CSV via AirDrop/iCloud Drive, Multi-language support

**Features:** Vision Pro support

**In-app purchases (1)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Unlock Pro feature | $0.99 | one-time |


### Units2Units

[App page](https://appshunter.io/ios/app/units2units/id6778024693)

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

**In-app purchases (1)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Lifetime Pro | $4.99 | one-time |


## Frequently asked questions

### Is Timer 555 Calculator free?

Timer 555 Calculator is free to download, with in-app purchases available.

### Is Units2Units free?

Units2Units is free to download, with in-app purchases available.

### Do Timer 555 Calculator or Units2Units have ads?

Neither Timer 555 Calculator nor Units2Units shows ads.

### Which is updated more often, Timer 555 Calculator or Units2Units?

Timer 555 Calculator ships an update every 3 months, and Units2Units every 6 days. Most recently, Timer 555 Calculator was updated on October 5, 2026 and Units2Units on October 4, 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.*