# Timer 555 Calculator Pro vs SPICE Viewer

The clearest difference is price: SPICE Viewer at Free against Timer 555 Calculator Pro's $0.99. Timer 555 Calculator Pro's advantage is in-app purchases (none vs 4) and iOS requirement (13.2 vs 18.2). On update cadence, ads and device support there is nothing between them.

SPICE Viewer is free to download; Timer 555 Calculator Pro costs $0.99 up front. SPICE Viewer sells 4 in-app purchases, starting at $0.99 per month. Timer 555 Calculator Pro asks for nothing beyond the download.

Timer 555 Calculator Pro ships an update every 3 months, SPICE Viewer every 2 months. The most recent releases landed on October 23, 2026 and October 13, 2026 respectively.

## The numbers

| Metric | Timer 555 Calculator Pro | SPICE Viewer |
| --- | --- | --- |
| Price | $0.99 | **Free** |
| Rating | **[4.7 (3 ratings)](https://appshunter.io/ios/app/timer-555-calculator-pro/id833443125/reviews)** | — |
| Number of ratings | **3** | — |
| Positive reviews | 100.0% of reviews | — |
| In-app purchases | **No** | Yes |
| Ads | No | No |
| Update frequency | Every 3 months | **Every 2 months** |
| Monetization | Paid | — |
| Size | 3 MB | 17 MB |
| Requires iOS | **13.2** | 18.2 |
| Devices | **iPhone, iPad, iPod** | iPhone, iPad |
| Age rating | 4+ | 4+ |
| Developer | [Siu Yuen Ho](https://appshunter.io/developer/814088527) | [AIP Technology Corporation, Taiwan Branch](https://appshunter.io/developer/1733199040) |

## What reviewers say

### Timer 555 Calculator Pro

[App page](https://appshunter.io/ios/app/timer-555-calculator-pro/id833443125)

Calculate parameters for monostable and astable circuits. Find component combinations for desired pulse width or frequency. Share circuit files via iCloud Drive or AirDrop.

**Highlights:** Calculate monostable pulse width, Calculate astable frequency, Find component combinations, Adjust component tolerance, Unlimited combinations (Pro), Share circuit files

**In-app purchases:** none


### SPICE Viewer

[App page](https://appshunter.io/ios/app/spice-viewer/id6758933278)

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

**In-app purchases (4)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Viewer(Monthly) | $0.99 | per month |
| Editor(Monthly) | $9.99 | per month |
| Viewer(Annual) | $9.99 | per year |
| Editor(Annual) | $99.99 | per year |


## Frequently asked questions

### Is Timer 555 Calculator Pro free?

Timer 555 Calculator Pro costs $0.99, with no in-app purchases.

### Is SPICE Viewer free?

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

### Do Timer 555 Calculator Pro or SPICE Viewer have ads?

Neither Timer 555 Calculator Pro nor SPICE Viewer shows ads.

### Which is updated more often, Timer 555 Calculator Pro or SPICE Viewer?

Timer 555 Calculator Pro ships an update every 3 months, and SPICE Viewer every 2 months. Most recently, Timer 555 Calculator Pro was updated on October 23, 2026 and SPICE Viewer on October 13, 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.*