# Timer 555 Calculator vs Simple Circuit Builder

Timer 555 Calculator and Simple Circuit Builder both sit at 3.9 stars, but that hides the real split: 100% of Timer 555 Calculator's written reviews are positive against 53% of Simple Circuit Builder's. Simple Circuit Builder's advantage is in-app purchases (none vs 1) and update cadence (every 3 weeks vs every 3 months). On price, rating, ads and device support there is nothing between them.

Both are free to download. Timer 555 Calculator sells 1 one-off in-app purchase. Simple Circuit Builder asks for nothing beyond the download.

On the App Store both sit at effectively the same score — 3.9 for Timer 555 Calculator against 4.0 for Simple Circuit Builder. Both are backed by a comparable volume of ratings — 8 and 28 respectively. Written reviews are what separate them: 100% of Timer 555 Calculator's written reviews are positive against 53% of Simple Circuit Builder's.

Timer 555 Calculator ships an update every 3 months, Simple Circuit Builder every 3 weeks. The most recent releases landed on September 24, 2026 and June 4, 2026 respectively.

## The numbers

| Metric | Timer 555 Calculator | Simple Circuit Builder |
| --- | --- | --- |
| Price | Free | Free |
| Rating | [3.9 (8 ratings)](https://appshunter.io/ios/app/timer-555-calculator/id834044557/reviews) | **[4.0 (28 ratings)](https://appshunter.io/ios/app/simple-circuit-builder/id1294616098/reviews)** |
| Number of ratings | 8 | **28** |
| Positive reviews | **100.0% of reviews** | 52.6% of reviews |
| In-app purchases | Yes | **No** |
| Ads | No | No |
| Update frequency | Every 3 months | **Every 3 weeks** |
| Monetization | Free with in-app purchases | **Free** |
| Size | 3 MB | 14 MB |
| Requires iOS | **13.2** | 14.0 |
| Devices | iPhone, iPad, iPod | iPhone, iPad, iPod |
| Age rating | 4+ | 4+ |
| Developer | [Siu Yuen Ho](https://appshunter.io/developer/814088527) | [David White](https://appshunter.io/developer/911163945) |

## 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 |


### Simple Circuit Builder

[App page](https://appshunter.io/ios/app/simple-circuit-builder/id1294616098)

This virtual lab offers a hands-on experience for learning about resistors and circuit resistance. Easily build and test series and parallel circuits, measure voltage and current, and understand the impact of component changes in real-time.

**Highlights:** Build circuits with up to eight components, Five component types, Virtual volt and amp meters, Adjustable resistor and voltage values, Real-time circuit analysis, Demonstrates 'Opens' and 'Shorts'

**Features:** macOS Compatibility

**In-app purchases:** none


## Frequently asked questions

### Is Timer 555 Calculator free?

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

### Is Simple Circuit Builder free?

Simple Circuit Builder is free to download, with no in-app purchases.

### Which has better reviews, Timer 555 Calculator or Simple Circuit Builder?

Simple Circuit Builder is rated higher. Timer 555 Calculator averages 3.9 out of 5 from 8 ratings, while Simple Circuit Builder averages 4.0 from 28 ratings.

### Do Timer 555 Calculator or Simple Circuit Builder have ads?

Neither Timer 555 Calculator nor Simple Circuit Builder shows ads.

### Which is updated more often, Timer 555 Calculator or Simple Circuit Builder?

Timer 555 Calculator ships an update every 3 months, and Simple Circuit Builder every 3 weeks. Most recently, Timer 555 Calculator was updated on September 24, 2026 and Simple Circuit Builder on June 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.*